|
|
|
Posted before but wanted to do a concise summary so here's another post. This is the most maddening problem I have faced in 20+ years of brick ownership and I'm hoping somebody will have some new ideas for me. Symptom is intermittent crank but no fire. I walk away and come back in 30 minutes it usually starts right up. If I unplug AMM it usually will begrudingly start in limp mode and get me home. Once there I replug AMM, clear code and then the rest of that day, the next day and maybe up to a week it behaves as if nothing is wrong. I've cycled thru the 2 good AMM's on the shelf, driving each one for several weeks and it acts the exact same with each one so I don't think it is AMM. I also had a hunch aboout the pre-pump so that is brand new (and the sock and hose) but that was not it either. So during the no start period:
1.) both relays in FPRelay are energized and closed
2.) 12vdc at fuse 4 during cranking
3.) 12vdc at both fuel pumps
4.) both pumps are operating or at least sound to be - jumped fuse 4 to 6 just to make sure with no luck
5.) noid light shows impulses being sent to injector 1 (didn't try 2-4 though)
6.)spark gauge on plug 1 in the dash (homemade lite gauge) shows spark during the no start period
7.) can feel squish of fuel in the return hose on the back of the FPReg with 4 and 6 jumped and also if I push the valve on the rail there is a puff of fuel/air coming out
8.) plugs get wet
Buggered up the threads on my fuel pressure gauge so can not measure the actual pressure at the rail but the "signs" are that it is good. So frustrating - all the ingredients are there but no start. I have not considered timing, compression air etc because I can't see these being so intermittent. Any ideas out there? My only idea is that maybe the ECU is altering the "mix" of the ingredients and changing the timing on me but this seems like a long shot due to the intermittent nature. Hoping somebody's got some ideas...
Robb McC
|
|
-
|
|
|
one hint over the ocean
we here in Germany know the Loizidis effect
for some components the ECU switches the circuit to earth
means at the component like AMM, pump, idle control you can measure +12 voltage
but his does not mean that there is current "running" through that component
as the ECU is not switching this component to earth
look at the diagrams
http://www.autoelectric.ru/auto/volvo/940/1993/940-93.htm
inside the ECU pictures you see the grouns symbol
happy searching!
Michael
|
|
-
|
|
|
Thank you Michael, Yes I am aware of this trickiness. And other trickiness like 12 v being present at a connector according to a VOM but with not enough current to even light a test light. Or how about the old crimp on connector connection that just stops conducting?
Robb McC
|
|
-
|
|
|
A thought along checking some connections.
I have not read the other post but try putting in a brand new rotor button under the distributor cap. There is a resistor embedded in epoxy that can become intermittent.
Also do not forget the Crank Position Sensor too!
These things can look good but play games with your head!
Phil
|
|
-
|
|
|
That's a good idea.
I had the same exact problem and it nearly warped my brain trying to find the solution.
I had spark at the coil but no spark at the plugs, and the problem was only showing up at random times.
I swapped rotor buttons as a last resort and the engine started and ran normally the first try.
If you're checking for spark, check at the spark plugs themselves.
The OP said that he had a test light rigged up inside the car, but if the resistance of the test light bulb is too low, the light may flash, indicating
normal spark while the coil still can't fire the plugs because of the high resistance (and resulting voltage drop) thru the rotor button.
I hope that made sense.
steve
|
|
-
|
|
"can feel squish of fuel in the return hose on the back of the FPReg with 4 and 6 jumped and also if I push the valve on the rail there is a puff of fuel/air coming out"
The "puff" part has me concerned. Sounds very certain you feel air or fuel vapor escaping when you invoke Mr. Shrader's relief. That should not be. Only liquid should be in that rail. However your note that plugs are wet when this happens doesn't jibe with vapor lock.
And the squish test I suggested last go'round doesn't really eliminate a regulator that occasionally sticks open. What threads are ruined? Those on the rail fitting or on your gauge adapter? I hope the latter. There's a recent post on TB (I'd link if the site was up) describing an eight-dollar adapter kit for the Bosch LH 14mm Volvo fuel fittings available from one of the tool companies.
My question, which you've probably answered (so please forgive my lack of research) is whether you've replaced the regulator with a Bosch. I say "with a Bosch" because I've read that others exist and they get trashed in the forums.
Also you say "both pumps are operating or at least sound to be - jumped fuse 4 to 6 just to make sure with no luck" and I find myself still wondering if you know both pumps are operating. Yes, I know you've said you have a new tank pump, but I know new does not equal working. When testing separately, do you hear them both? Is the main pump running with a smooth hum?
--
Art Benstein near Baltimore
"Do not machine wash or tumble dry" means I will never wash this ever.
|
|
-
|
|
|
OK, given your last response, I totally agree with you, and want to dismiss fuel as the cause of the no-start. The FPR would only be a suspect in my mind if that puff you felt was thought to be vapor. And this wouldn't be a problem starting cold. Wet plugs (wondering how wet) dismiss that too, or point to a possible flooding condition, which I think you are experienced enough to detect with your nose and foot down on the pedal.
That leaves spark. Is it still occurring? Is it occurring at the right time? Maybe, if you can, set up to crank from under the hood, so when it happens next time you can get your timing light on it and catch it NOT firing at TDC during cranking.
As to the cause, I have had a suspicion for some time a gob of green goo corrosion in a battery cable could cause the starter to drag the voltage low enough to reset or confuse the EZK during crank time. You'd still have spark, perhaps, but timed ineffectively. A jump wouldn't reveal this, and it might take a good ear to detect it in the cranking rhythm. A timing light would catch this.
--
Art Benstein near Baltimore
There's no worse feeling than that millisecond you're sure you are going to die after leaning your chair back a little too far.
|
|
-
|
|
|
You're giving me some hope Art (along with the other message below from Machine Man and Hillbilly). I will set up the timing light right after I go over every connector and battery cable in the car this weekend. I'm thinking my spark light could be wrong and that is where I should be concentrating now. Resister in the rotor?? Never heard of that but I have a new one on the shelf and will try it but of course I will have to smash open the old one just to see for myself - this sounds too perfect an urban legend. I must pull out my notes again from 2009 in that car's glovebox because this is all playing out strangly the same as then and my memory is it just went away but maybe there was something I did then that changed the behaviour.
Robb McC
|
|
-
|
|
|
Yes, the resistor in the rotor is a very good idea. Not because it would be intermittent, but when it opens, the spark has to jump across that additional air gap, and that makes everything ignition-wise marginal. And while cranking, that's when you need it to be reliable, not marginal.
That was one of the very first Volvo fixes I had to do. My daughter's 83 -- our first Volvo -- was a no-start because of that rotor. I had just brought home our second Volvo and her car was just two blocks up the street, so I snagged the rotor from one to put in the other. I think the good one measured about 1K ohm between contacts. The bad one, infinite. Anyway, it is far easier suggestion to try that first if you can.
Of all people, I should not assume ignition suspects start out with new cap, rotor, wires, and plugs. That's what they call a tune-up these days, I hear.
--
Art Benstein near Baltimore
Shirts get dirty. Underwear gets dirty. Pants? Pants never get dirty, and you can wear them forever.
|
|
-
|
|
|
Thanks Art,
I think I've fully turned my hat around from the side that says Fuel Chaser to the side that says Spark Chaser. Removed and went over every connection related to starting/running last night especially the big fat ones from battery to starter and alternator to starter and all is clean with no green that I could find. Put the timing light in the trunk and repainted the timing mark on the pulley so next time it happens I can really check for spark (now thinking my homemade gauge might not be fully accurate) and also the timing. Also went ahead and ordered a full ignition set (plugs, wires and cap - gonna use the new rotor on shelp) as I looked and it had been 25k miles so it can't hurt. I like your theory the voltage getting dragged down because it explains one thing I have been wondering about which is why does it never cut out while running. I'll post back when I know something.
Robb McC
|
|
-
|
|
|
OK, just want you to be aware; the green crud can live hidden inside the big crimp lugs at the starter and especially at the battery. Some have found it at the block lug. Those are the spots. The alternator is not involved with starting. I've seen it inside the wire insulation and only just perceptible as a bulge in the cable.
And as far as crank vs. run, well every ignition component is much better off with the engine running, even with normal battery voltage available. If there's to be a weakness fault, it is going to show up as a starting problem most every time. Your light monitoring spark may be working very well, but you have no way to tell if the timing of that spark is coinciding with the piston reaching TDC on the compression stroke. That's why you need to catch it with the light.
If, when you test this out, you can't get it to fail, try removing the injector plugs and use the timing light on the coil wire, so you get a flash at both points on the diameter of your crank pulley. You may even want to mark the opposite side. Then if you ever see a flash not coinciding with a mark, you know the EZK is messing up when that happens. Have a battery charger and an afternoon to play.
--
Art Benstein near Baltimore
"Bigamy is having one wife or husband too many. Monogamy is the same." (Oscar Wilde)
|
|
-
posted by
someone claiming to be Robb McC
on
Sat Jul 13 17:50 CST 2013 [ RELATED]
|
|
Just went out and split back the insulation at all 4 of those cable ends (+ - battery and block ground and + at starter) and no green to be found on the wire or inside the lugs. I did set up a vom on the battery and noted when I start to crank it dips to about 10 v then back up when it starts to 14. I wonder if that is normal. Darn I'm tempted to separate out both cables from battery to ground and battery to starter and look for weak spots or bends now. Of course it's starting fine today, this is just in preparation for the next time it does not start. So do you think dropping to 10 v for a second is significant?
Robb McC
|
|
-
|
|
|
You might want to get the battery load tested.
Dan
|
|
-
|
|
|
Thanks for jumping in Art - no puff is perhaps the wrong word, I did not feel like there was air coming out just fuel and just eyeballing the volume of the rail it seemed like the right amount for about 35 psi. The threads on the HF pressure gauge are toast - brass too soft, I guess I didn't expect it to last too long but 4 or 5 times on and it was toast.
Yes I've operated both pumps during the no-start time from the fuse box with fuse 4 removed and can hear them running one at a time, first power to the left then to the right. Main pump hums pretty smoothly. In my mind I have 2 buckets, one says "could be intermittent" and one says "probably not intermittent" and I guess I had the FPReg in the probably not but when I get home I will swap the regulator out with one from the 740 (which has never not started for its entire 21 years since assembly in Belgium in 92) and see what happens.
This no start will very occasionaly happen from a dead cold at morning temp of 70 or so, so probably not vapor lock. The next move seems to be into "subjective" - take a plug out and check for blue spark (maybe my dash spark gauge is too sensitive) and get another pressure gauge and leave it connected so I know for sure there is at least 35 psi when it won't start. I had trouble before with gas leaking out the schrader valve before though no matter how much teflon tape I used.
Robb McC
|
|
-
|
|
|
Just one thing have you checked the main fuel pump check valve it could be letting fuel drain back into the tank.
|
|
-
|
|
|
Well, sort of - when my fuel pressure gauge was working and I attached to the schrader on the fuel rail I observed that the leak down rate was very very slow (this was not during a no start period mind you). It was holding 20 or 30 psi for 30 or 40 minutes so I believe the check valve is good. Also the main fuel pump is only about 2 years old. Now could the check valve go intermittent? Doesn't seem plausable. I do like your idea of cleaning every single electrical connection on the car related to starting and running which I will put on the list for this weekend. The labor in that seems like chump change compared to what I've already put into this over the last several months...
|
|
-
|
|
|
Remove the back cover of the ECU connector at the ECU so you can access the pins. When you get the no-start condition, check the resistance from pin 13 to ground (coolant temp sensor). You should get somewhere in the neighborhood of 1500 Ohms resistance. An open circuit at the coolant temp sensor will give you a no-start for sure. Also, the main/fuel press relay can be functional but weak/dirty contactors can be as bad as an open circuit. Make yourself up a "Y" jumper with 3 male spade connectors, remove the relay entirely, and jumper across the contactor terminals at the relay connector (I forget which ones, but the relay should have a diagram on it to help you figure it out).
Steve
|
|
-
|
|
|
Steve - I will check the resistance at the ECU but doubt the coolant temp sensor could be at fault because I do have spark during the no start period. Also there is no way this could be FPRelay related - I have run it several weeks on 2 different FPR's from the other bricks with no change in the behaviour. Also just to be sure I put a brand new one in (made in germany) from eeuroparts about a month ago with again no change in symptons. Thanks for your thoughts and time
Robb McC
|
|
-
|
|
|
These things are always hard to find. Sounds like you have done a lot of things. I would have a close look at that fpr and check all vacuum hoses especially the one on the fpr check the full length of the vacuum hoses not just the ends. Clean all earths on wiring in engine bay and inside cabin. It wouldn't hurt to buy some dielectric grease and unplug all electrical connections and clean them and grease them up with the dielectric grease. Clean the ECU terminals as well in the cabin.
|
|
-
|
|
Hi,
Does this mean the vacuum hose has gas in it? If it does have gas in it, then the fuel pressure regulator has failed, and is flooding the engine after shutdown. Not sure why unplugging the AMM solves the problem, though. However, a failed fuel pressure flooding the engine would explain wet plugs and no start with spark.
Goatman
|
|
-
|
|
|
Sorry I wasn't more clear - this has the schrader valve on the fuel rail and during the no start period if I put a tire pressure gauge on there I get a puff of fuel/air so it seems pressurized. There is no fuel at the vacuum line on the FPReg. When I had a functioning pressure gauge that I attached to this valve it showed about 36 psi, with about 45 psi when I removed the vacuum hose on the FPReg. Then the leakdown rate was very good - 30 minutes after shutdown still had 20 or 30 psi. But being cheap HF material I buggered up the threads putting on so many times and now don't have it during these no start periods.
|
|
-
posted by
someone claiming to be Robb McC
on
Wed Jul 10 17:43 CST 2013 [ RELATED]
|
|
Should I try a PnP ECU? I don't have any other ideas but surely there is something forgetting in meager no start time...
|
|
|
|
|
