Hello. First post. I have a 1981 Volvo GL B21F K-jet NA with an IPD VX cam and adjustable cam timing gear. 500K miles. It's been a hangar queen for the last 6 months because of a hard-to-start issue. I've done a ton of work on it. The fuel pressures (by CIS gauge) are all within Volvo specs, and the fuel flow is good. The fuel filter is new, the pressure plate is adjusted and seems to work correctly, the air-fuel distributor is cleaned, the valves are adjusted, injector seals and holders are new, most all of the vacuum hoses have been replaced. The charcoal canister is bypassed, and the cold enrichment part of the CPR is open (my ported vacuum switch is broken and I can't find another one). I installed a Volvo pulse relay for the cold start injector. O2 sensor connected or not seems to make no difference. The boot is tight and the intake manifold gasket is new. All of the flame trap parts (including the oil trap) are new. Before this last round of work I did a compression test and all 4 cylinders were within spec.
None of these things seem to have had an effect, except that now I can't get an idle below about 1200 rpm. I've had to adjust the little screw on the throttle linkage just about all the way in, which means the micro switch on the Constant Idle System never engages. I've attached a vacuum gauge to the manifold on the front port (where the vacuum line to the ported vacuum switch would normally go). When I crank the engine the vacuum needle barely moves. It swings a little in concert with the engine cranking, but it doesn't seem to do much more than a couple or 3 inches of vacuum. When the engine finally starts (which is usually accompanied by much gas pedal pushing) the vacuum gauge will eventually get to maybe 16 inches at around 2K rpm. Sometimes I need to take it to 3K to get the vacuum to settle down to a steady reading. Occasionally I can get it to sit at around 1500 rpm and just run for a while, but usually I have to stay on it with the gas pedal to keep the engine running. If the engine speed drops to around 1100 the vacuum drops to around 6 inches and the engine will start to sputter, while the vacuum gauge goes crazy at the low end. Sometimes I can catch it by pumping the gas pedal but usually the engine just dies. Trying to re-start it is harder after that.
I've done a lot of manual movement of the pressure plate. With no control pressure present the plate is easy to lift with no restrictions, and does the little bounce thing when I let it go. With the fuel pumps running it is harder to lift but it doesn't have to go very far to get the injectors to spray. When I crank the engine with the injectors out and the holes plugged, I'm lucky to get a few spurts of gas out of them, but the cold start injector seems to work fine.
Right now I'm thinking this is a vacuum issue. I haven't been able to find what the normal "cranking vacuum" spec is, but it's hard for me to think that just a few inches is enough to push up that pressure plate, especially when the warm control pressure has kicked in.
Thanks in advance for any words of wisdom that could help me.
I was just fighting my 1980 242 DL with the same issues, does it have the a/c solenoid on the firewall? You can't plug these lines as the vacuum operated idle control valve that bumps the idle is activated by a lack of vacuum. In other words it needs vacuum supplied to it to operate at low idle. I found one of the hoses going to the valve was a S.A.E. size so it would leak just enough for the idle valve to operate intermittently. Once I zip tied the vacuum line to seal up the leak the car has idled wherever I adjust it to. I did the electric fan conversion and installed the 100 amp alternator from a 740. Since the a/c hasn't worked in years, I have that solenoid hooked up to the fan relay so that it bumps the idle when the fan comes on.
That's a great thought. Even though both my 81 New Car and Wiring Diagram greenbooks show what you're talking about mounted on the firewall, on mine there's just nothing there. With the Constant Idle System I think it's all electrical, getting voltage from a wire connected to the clutch coil for activation for increased engine RPM. As I mentioned in my response on this thread to Phil, my car is a late year 81 and has some features of the 82 models. I kind of like your system better, though.
I did the electric fan thing, too, when I replaced the radiator in 2002. I used a fan out of a 1990 Cutlass Sierra 3.3L. It fit so perfectly onto that Nissin radiator. But one thing Dave B. doesn't talk much about on that conversion is the power usage. It sure surprised me. I originally wired mine so it could continue running for a while even with the engine off. Thought it would help cool the radiator. Instead it just killed my battery. I upgraded to a 90-amp alternator, and moved the fan hot wire so it would stop with the engine. I also ended up wiring in a console switch so I could just shut it off if it decided to fire up at an inopportune time. Now it's got some kind of intermittent problem. Sheesh! I may just go back to the clutch-driven fan.
I have a stock 81 California B21F with Bosch ignition and CIS. I'm a bit rusty on the kjet inner workings so I'll have to look that up again.
I understand you to say:
-good compression
-pulsing vacuum at idle
-difficult to start and keep running
-vacuum switch to the CPR and ignition is broke so switch is open or closed?
-kjet pressures are ok but no control pressure?
-vx cam with unknown timing?
-injector patterns good and new seals
-ignition timing good?
1. I tested the engine compression a while ago by time, but it's been only maybe a hundred miles or so by driving, since the car's been in the garage so long with this problem. The readings were #1 - 155, #2 - 160, #3 - 160, #4 - 160. When I tested the valve lash recently most of the measurements were at the low end of the checking specs, which indicates some valve seat wear over the past 90K miles since I installed the VX cam and last adjusted the valves. I adjusted all of them to bring them up to the wider end of the adjusting specs anyway, but several of them used the thinnest shims available. The next time they need adjusting I know I'm looking at at least a cylinder head re-build.
2. The pulsing vacuum occurs while cranking, before the engine actually fires up and tries to start. Once I work my program hard and get the engine actually running, the vacuum holds steady at whatever speed I can keep it at. Until the engine starts to die if I let the idle fall too much, at which point the vacuum needle just goes all over the place. There's a very small amount of needle wiggle with the engine running at a constant speed, but I understand that is normal with a more aggressive cam. My main concern right now is that the vacuum readings, both during cranking and while running, seem too low to me.
3. Yes, difficult to start and keep running. Before this last round of work it tended to start a little hard when cold in the morning, but it still started. And it ran and idled fine once started. But if I tried to re-start it within several hours it was almost impossible to start. I would crank and crank, sometimes it would sputter and backfire and then die. Usually if I walked away from it at that point and smoked a cigarette and then went back and tried again it would start up OK. This made me think it was a warm start issue, which normally points at K-jet rest pressure problems. Now I think what was happening before was that the engine would start as long as I got a lot of gas from the cold start injector, even without much contribution from the main injectors. But if the engine was still warm and the cold start injector didn't put much gas into the manifold, there just wasn't enough cranking vacuum to get the main injectors to work at all (I think). Currently, it's just hard to start and almost impossible to keep idling at anything below 1100 rpm. As it falls below 1500 or so there's a rebound effect where the vacuum goes way down and appears to be insufficient to keep feeding the main injectors. If I pump the gas pedal hard sometimes I can keep the engine running, but just as often it just dies.
4. Yes, the ported vacuum switch (PVS) to the bottom part of the CPR (I think it's called cold acceleration enrichment) is not in the car. This system only operates at coolant temperature under 53 degrees F anyways, other than that it has no effect. I'm not sure what you mean by the ignition, my CPR only has one electrical connection that is used to heat up the bi-metallic spring in the CPR to increase the control pressure after a few minutes, which leans out the mixture after initial start-up. As far as I know the top part of the CPR which has to do with the basic control pressures is working fine.
5. I have tested all 4 basic K-jet pressures and all appear OK. The line pressure is 68 pounds, the cold control pressure is around 30 depending on ambient temperature (it's been around 70 degrees here locally), and the warm control pressure goes up to around 56 within 5 minutes. All 3 of these hold steady once established. The rest pressure goes down to around 30 at first, and takes at least an hour to fall to 20. All of these are very close to Volvo specs.
6. Yes, VX cam. I've varied the cam timing to plus or minus 4 degrees.
7. These are old injectors. I've tried blowing carb cleaner thru them with my air compressor using the regulator. The patterns look fairly good to me now. They seemed to open at about 40 psi on the air compressor and closed at less than that, which I believe is how they should work. Both seals and holders are brand new.
8. My ignition timing is currently 10 degrees, which is 2 more than the spec, but less than the 14 mentioned by the guy at IPD.
The adjustable timing gear worries me. You may have too much valve overlap going on and not getting a good pump down vacuum from the cylinders.
I would try pinching off the vacuum hose to the brake booster as you may have a bad booster or check valve and not know it yet.
I did not know that any K jets had Constant Idle Control valve until it all changed in’82. I thought they only had an auxiliary air valve for warm-ups. This ’81 might be a hybrid year for all I know!
I have three other cars with LH systems. It has been a while since I looked at my 78 but the switch, I think it has, is suppose to click at throttle opening. It is adjustable by two screws and rotating it with the throttle closed.
I do not understand the Control Pressure Regulator condition as how you mean it is open. There are electric heaters for warming up on it as well as the auxiliary air valve. There is a thermal cutoff switch for the cold start injector, so when it cranks when warm, it will not work.
The ported vacuum switch leaves me in the dust as to what you are describing.
I will be back to check up on the other posts about this car!
Phil
You're probably right about my car being a "hybrid". I'm the original owner. I bought it in Germany and picked it up in New Jersey on 2 Sep 81. I had ordered an earlier car but I was delayed in returning to the States so they shipped a later car for me. I believe this one was assembled in June of 81, and the invoice says "California specs". It's definitely not an MPG version (no Chrysler distributor), but it seems to have a few elements of an MPG. At least I was always proud of the 30 mpg highway I was getting! I think it was assembled when some features of the 82 model year were being introduced at the factory, but it's still identified by VIN and glass labels as an 81 model.
I agree with you about the concern on the cam shaft gear, as well as the cam shaft. There's controversy about the use of the VX cam on K-jets. An aggressive cam will reduce vacuum. When I put it in back in Jun 03 IPD indicated that it was applicable for the K-jets. I note that now they have dropped all K-jets from their compatibility list, but there is a comment that K-jets will idle rough with it installed. I recently called IPD and talked to someone (I forget his name) who seemed pretty good on the K-jet. He looked in his database and the only entry he could find was a customer comment that it seemed to work best with the ignition timing set to 14 degrees. Right now mine is set at 10 degrees. I've always had problems with this car when changing the timing belt. I can easily find the alignment marks for the cam and crank shafts, but even after all these years I can't find an alignment mark for the intermediate shaft. My Chilton's says to set it at 4 o'clock, but at least one of my Greenbooks seems to show 3 o'clock. I remember I used to set it somewhere around 4 o'clock, but then something changed and it wouldn't start there. It's almost like a mechanic (when I was paying for service) pulled the distributor to make it time right.
Anyway, the IPD guy was really sure that the cam isn't my problem. I know it seemed to work fine for years after I put it in. There was no radical difference, but I did get a performance improvement in the mid-range, which helped out on the interstate hills heading toward DC when I was working.
The cam timing is also an issue. From what I can tell on the web, most people think that advancing the cam timing should improve vacuum a bit. I talked to a foreign car mechanic yesterday who said retarding the cam would help vacuum. I've tried 4 degrees both ways, and haven't been able to tell a difference yet.
My comment about the open CPR was referring to the vacuum lines. One of the nipples on the blue-top ported vacuum switch under the number 2 intake broke off. I tried one from a junk yard, but it doesn't work. Mine probably wasn't working either. I haven't been able to identify a current replacement. It's a 2-port switch with a 3/8 inch pipe thread that activates at 53 degrees F coolant temperature, closed above 53 and open below 53. If anyone has a part number from Airtex or Standard for a replacement I would certainly get one. In the meantime I just plugged the coolant hole in the block and the vacuum port on the manifold (unless I have the vacuum gauge hooked up), and left the vacuum line on the CPR unattached. From what I understand the purpose of the system is to lower the control pressure upon acceleration when the engine is cold so as to enrich the mixture for a short time. Normally the pressure on both the top and bottom of the lower part of the CPR is equal so it has no affect, so I figured I would just leave it like that for now. This has nothing to do with the top of the CPR and its heating element for producing the warm control pressure. All of that appears to be working as designed on my car.
I believe the cold start injector works for at least a second or so no matter what the temperature is. At least mine does. Of course it runs longer (as controlled by the thermo-time switch) when it is cold. I'm not really sure how this relates to the pulse relay I put in recently. It's spec'd for turbos and 6 cylinders and is supposed to help with warm starts by pulsing the cold start injector with short bursts for a while. I don't know if it works simultaneously with the thermo-time switch activation, and I don't know how long it works. I'm not even sure yet if mine works at all. It's a simple wiring job, but maybe my cold start injector isn't designed for pulsing. I note that there seems to be different cold start injectors spec'd for turbos and NAs. It does seem like my car will start on its own now, eventually. Before, I could get a cold start (with difficulty) but after a few minutes the only way I could get it started again was to spray ether into the air intake. Like it just couldn't get enough gas on cranking once the higher warm control pressure kicked in. While playing with the injectors out of the car, I found that I could get a second or 2 of engine start just from the gas coming from the cold start injector alone as long as the control pressure was at the lower cold level.
The reason I mis-adjusted the screw on the throttle linkage was that I can't get the car to start at all even while pumping the gas pedal vigorously, because the engine RPMs would drop too low while my foot was off the pedal. By increasing the minimum throttle idle position at least the engine speed won't fall off as much between gas pedal pumps. The side affect of this is that the micro-switch is beyond its activation position now for the Constant Idle System. Before this last round of work I went thru the Volvo troubleshooting procedure for the CIS and everything seemed in order. The point now is that my idle problem, whatever it is, can't be corrected even by an operating CIS because the engine just won't run below 1100 rpm and the CIS wants it to be 700 rpm (manual M46 tranny, by the way).
I'll definitely try your idea about the brake vacuum booster hose ASAP. My check valve is fairly new so I'm familiar with the pop sound it makes when it fails, but it's worth a shot.
Sorry for the length and rambling on this response. I see so many threads on this site and others about "my brick won't start" and it seems like there's always a different solution. Sort of like asking why your cat won't use the box. There's a hundred different anecdotal well-intentioned responses, but chances are your cat is different. I was really hoping that by getting some quantified numbers on my problem I could get closer to an answer. Maybe not.
Thanks for the new ideas, Phil. I'll get back to your *long* post when I get back into town from seeing the doc.
My injector seals and holders are all brand new. I did that when I stuck the injectors back in the engine after doing all I could with the fuel gauge and lifting the pressure plate to watch the injectors squirt thing.
I was so optimistic that I had this licked when I saw a little action out of the injectors when cranking the engine after adjusting the valves and advancing the cam timing. Obviously I was wrong.
You know, Phil, what I was really hoping from starting this thread was that someone out there with a car similar to mine (but with a stock cam) would get piqued (or just have pity on me) enough to actually dig their old vacuum gauge out of the bottom of their toolbox, pull their coil wire or fuel pump relay, and do the "cranking vacuum" test like I did. It amazes me that there are just no specs or descriptions of what the manifold vacuum actually looks like on these K-jet engines during cranking. I have read that the system uses the cranking vacuum to start. I just don't know how much, and evidently no one else does either.
I started mentioning this recently to a guy at the local Advance Parts. Before I could finish my sentence he was ready to sell me an aftermarket vacuum canister, because it seems the only people who talk about this are those with aggressive cams and big engines who discover afterwards that they don't have any brakes due to the lower vacuum. But at least their car starts.
I don't know that this is my answer, but if I had something to compare mine with I could know if I'm barking up the wrong tree.
Thanks again for your continued interest. I'll get back with you later.
OK, I haven't learned yet how to focus the little camera in video mode. What it doesn't show well, is the needle barely makes 2-3 inches vacuum while cranking, and at 40 degrees F, the idling vacuum (fast idle) doesn't quite make 15 inches. This was a cold start.
Here's the gauge in the clear, so you can at least guess where it reads...
...I've been lurking on this thread out of interest, and am not clear on what part cranking vacuum plays, when you say:
"I have read that the system uses the cranking vacuum to start. I just don't know how much, and evidently no one else does either."
It sounds like the theory is that vacuum is needed to "suck" the airflow plate up (higher) for starting. I don't recall reading that anywhere, and have assumed till now that the plate movement is purely determined by airflow and counterbalanced by control pressure on the plunger.
Frankly if that vacuum theory is correct, I'd need some convincing. But I don't want to muddy this thread any further, other than a brief response if possible.
P.S. I may have that blue thermo-valve if your interested. Also quite a few airflow meters and some fuel distributors acquired several years ago from DM Engineering in CT, who developed the Volvo turbo in 1979 and '80.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
Maybe I've gotten further into this thing than is good for me. But here goes:
If you go to the K-jet.org 200 series Greenbooks, under the K-Jetronic section, for TP12043-4, CI Fuel Injection System Construction and Function, on the bottom of page 6 it says "While cranking, the engine cylinders develop a vacuum which causes air at atmospheric pressure to flow through the intake system. This air passes through the air flow sensor" [aka the pressure plate] and on into the manifold.
You're right in that vacuum doesn't "suck" anything, rather it creates an area of lower than atmospheric pressure on top of the plate, and it is the relatively higher atmospheric pressure below the plate that "pushes" the plate up. Very similar to how lift is produced by an airplane wing. But without the vacuum-produced lower pressure on top, both sides of the plate would just see atmospheric pressure and it would never move.
This is why K-jets are so exquisitely sensitive to air and vacuum leaks. They expect to see the vacuum and air flow conditions that the designers intended. Any disruption to this and the K-jet can't compensate. And that is one reason (other than fuel economy) the K-jets were superseded by the electronic injection systems, which can be programmed to compensate for less-than-optimal conditions.
Hope that helps at least a little.
And yes, I am interested in getting a thermo-vacuum valve [aka ported vacuum switch]. Maybe you could private message me.
Thanks for your kind response to my senior moment analysis of your symptoms. You are right of course. But your case does remind me of my most recent K-Jet no-start, on a turbo several years ago. It too had been a hanger queen for a long time.
In brief, it would start for a few seconds, then die. Turns out it was starting on CSValve fuel, then dying due to a massive vacuum leak -- air boot was ajar, from some previous work probably.
With a smug self-satisfied smile I confidently tried the key, but got the same CSValve start, then nothing.
Further nosing around revealed a disconnected Idle Air Valve hose. Why and for how long I couldn't say -- call it the hanger queen effect. Putting that hose back on cured the problem.
It sure sounds like your situation was similar to mine. So you might want to double check that "tight" air boot, and take a look as the CIS air hoses too.
I see Art has joined the party. Things are looking up IMO.
Bruce
P.S. A quick look in long-neglected places failed to turn up that thermo-valve, but I'll keep at it. Most of those old places are hard to find, since the garage is now overrun with Suzuki bikes.
--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.
You know, Phil, what I was really hoping from starting this thread was that someone out there with a car similar to mine (but with a stock cam) would get piqued (or just have pity on me) enough to actually dig their old vacuum gauge out of the bottom of their toolbox, pull their coil wire or fuel pump relay, and do the "cranking vacuum" test like I did.
Yeah, those were my exact intentions both yesterday and today. One more honey-do and I'll get 'er done. Today.
--
Art Benstein near Baltimore
"I don't think you can get cold in Volvo 240 series. The AC can't do it and the heater won't let you." -darkdelta
Thanks for the long post. I feel better that you wrote one as I do it all the time. It is nice to have comrades with fingers and thoughts.
The timing belt replacement can be tricky if your metal cover is dirty on the inside.
You see the timing mark is actually a formed bump or crease. It runs back horizontally and is on the inside of the metal cover at the three o’clock position in relation to the distributor or intermediate sprocket.
You have to use a mirror to look down the length of the tooth with the punched dot on it. If you run your finger along the right on the inside of the pan, you can feel it. You cannot see it without the mirror and it has to be clean down there too.
The rotor of the distributor should point to number one wire or the notch on the distributor. The dot on the sprocket will be at the formed crease when the belt it is installed.
The line on the belt will have to an estimate to lie over to the notch going to the crankshaft. The line is about three belt teeth above engagement with the crankshaft sprocket.
Main thing is camshaft to distributor be on their marks with the belt taut between them and around under the crankshaft. With those three, locked in step, you are good. The line of the belt as to the crankshaft will be up above and away from contact with the sprocket by those three teeth but is ok anyway.
If you install it taut around the right side, you do not have to have lines. They are confidence makers unless you over think the crankshaft line, a little.
IPD sells decent stuff and sometimes for decent prices. They do like to tweak things but I am not into that. I am a conservative chap and I have witnessed many modifications as a total loss of investment as they make a car to personal for someone else. Cars are, IMHO, the worst investment on earth, just because of the business of the insurance industry.
The part about mid range improvement means they adjusted the power that the engine was going to make, low or top end, to a place that a customer might like to use it more. It depends on the type driver you are, if you are happier.
The part about retarding the timing will affect vacuum. Ignition and cam timing work together as power and economy do not always match up like the drivers. Think of how muscle cars idle.
You are right to have high vacuum and for streetcars, a steady vacuum is nice with a price.
You have the problem of excess air or the lack of its control. I would be suspicious of the intake manifold gasket and the flame trap and its hose system back to the throttle plate. A leaky intake valve should also be a contender when vacuum is an issue or a sign on the gauge but the compression test you did kind of pooh-poohs that.
Do you still have a frequency valve on this car? Is it buzzing! It is a Big deal if it is not. There used to be a relay that hooks it and the 0-2 sensor to the computer. It was on the driver’s fender next to the headlight relay.
You said it has California spec. so it must have a Lambda-sond system. Just wondered why they were even messing around with a vacuum port in the coolant to the pressure control. The 0-2 sensor and the computer will adjust the frequency valve for self-tuning. I think it is how my 1978 works.
I think they did away with a switch on the fuel distributor vane. They went to several throttle switch configurations to tell the computer when to idle. On the 1978 it had settled down to the one used on all the later cars. It is very important for the off idle response transition.
In your case, you need to get down to the idle range to know if it works.
I will try to check back later as the conversation should get shorter the closer we get to the problem(s).
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