Hello Brickboard

I have been picking away at my 1974 145 with a kjet B20F for a while now. It had been sitting for nearly 30 years so I have had my work cut out for me. Nearing the finish line now but faced with a new problem.

The car idles well and steady at 900 rpm as per the green book but will not rev smoothly. If I give it some gas it will slowly ramp up in speed but nothing steady. There is some popping occasionally on deceleration. Unfortunately the car is not drivable in this state. Gutless is what my Dad would have called it.

I have set the timing at 10BTDC at 600 rpm as per green book. There is good compression on every cylinder. I have checked for air leaks everywhere I can think of. I ran a test on the injectors (which were new last week) and they are equal for flow across all four. The system pressure is running a steady 70psi. Control pressure is also good and rises to around 52-54psi when warm. Using premium gasoline with no ethanol. Brand new fuel filter.

Does anybody have any ideas? I have some time off work this week and would love to get to the bottom of this.

As always, any guidance would be gratefully received. Thank you Brickboard.

Any chance you have some flat camshaft lobes?

You can have worn camshaft lobes and still get decent compression readings.

Volvo had to replace a batch of bad camshafts for the later B20s.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

that is something that had never occurred to me and to be honest i have no idea how to test for that. how would i work it out? the car has very low miles. is it something that was a fault from the factory or related to wear?

Pull the valve cover, remove the positive power wire at the ignition coil and isolate the wire to make sure it can't touch anything.

Make sure the car isn't in gear for a manual transmission or in park for an automatic and that the parking brake is set, then have someone turn the ignition key to start and check to see if any of the rocker arms aren't moving as much as the others.

If you can't get someone to help, get or make a remote starter switch and connect 1 wire to the starter trigger wire and the other to the the large wire or pole on the starter.

I'm not sure if it was an official recall, but Volvo had to replace under warranty a large batch of camshafts for the later 140s as they were wearing prematurely.

It's possible your engine never got the replacement camshaft.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

Eric, it's quite likely his '74 140 didn't get or need a new cam. I don't think many, if any, of the '74s such as mine, had the problem cam even though they were listed as a possibly affected year. It was likely listed as all B20F production years not knowing exactly when the the last of the bad cams had been used in production at the various plants, even the parts chain. There may have been no identification to distinguish them, just the ship date and last VIN before the problem was identified. Even if his did have one, they started to show wear quite quickly and I'd expect it would have needed replacement long before now.

I bought my '74 new and I remember the cam issue not being an actual recall, rather a TSB to dealer service. It would have been to inspect the cam lobes for signs of premature wear whenever checking/adjusting valves such as at the major service intervals. The cams would of course been covered under the normal warranty, but these were fairly short then, like a 24 months powertrain warranty?

I was aware of the problem and used to check/adjust my valves at every oil change, so inspected for cam lobe wear for a few years until I finally felt comfortable I didn't have the bad cam. Something in the back of my mind at the moment recalls the warranty may have been extended for the cams, like an extra 2-3 years, which is about how long I kept checking. My indie had shown me a bad one he had and what to look for. I do recall it soon became fairly well known the problem mostly only affected up until mid/late '73 model year production, leastwise here in Canada with ours from the Halifax NS assembly plant. As I recall, US 140s were mostly Sweden back then, so your experience may be different. I sold my '74 144GL in 1989 at 175K mi, still happily with the original cam.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Thanks for the guidance. I will try this at the weekend

If you remove the valve cover you'll be able to see each rocker and pushrod going through their motions as you spin the engine through a few cycles turned by the crank bolt. - Dave

You haven't mentioned checking or replacing the fuel accumulator. It could easily be full of gunk and restricting fuel delivery at high demand to cause symptoms such as you describe. It should be located underneath, mounted next to the main fuel pump. In the fuel delivery system it's between the main fuel pump and fuel filter. It's purpose is to help smooth out pulsations in fuel pressure. It also acts as a backlflow preventer to maintain system pressure when the engine is off, also helping to prevent vapour locks.

It's a simple design, a fuel chamber reservoir with a spring loaded diaphragm that responds to fuel pressure. Any gunk around the diaphragm or fouling the large spring could cause fuel delivery issues, acting as a flow limiter. It's a sealed unit and generally not considered serviceable. You could try bypassing it for testing purposes if the output fitting matches the fuel pump, which as I vaguely recall from others it does.

Bosch p/n 0438170001 is for 1974-on 140/240 K-Jet and commonly available from Volvo aftermarket suppliers, also on places like Amazon. It's not overly cheap, so do shop around. RockAuto carries it and is one of the better sources. A number of other makes with K-Jet use the same one.

Going back to thinking about the fuel distributor. Some of them have a small filter screen insert in the fuel line ports, possibly just the intake port, I forget. That's another well known place for fuel flow restriction.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hello Dave. Thanks for the response. I should have mentioned that I replaced the accumulator with a new one. I had to replace everything from the tank onwards. Had the tank refurbished, new accumulator, new pump, all new lines, new filter, new injectors, new injector lines.

I have noticed something new when working recently though...when I do get the car to rev, the exhaust gets much stronger in smell, making me think that it is burning rich. I do wonder if the fuel distributor may be the problem because it is the only thing left in the chain, but it is strange that it seems to be giving too much fuel. I would have expected starvation. Maybe it is an air thing, but I can't think what. New air filter, and, last time I looked, no rodent nest or anything weird. Perhaps it is worth taking another look on the air intake side?

Unless you find a nest hiding in the airbox intake, it's hard to imagine air starvation as long as the air plate floats easily and the exhaust isn't plugged. My chief suspect at the moment would now be a stuck plunger in the fuel distributor, as you've previously considered. It's not that uncommon, even more so with yours having sat so long, and would very much correspond to your symptoms. Manually lift the air plate and if fuel flow to an injector doesn't noticeably increase then it's stuck.

The exhaust gas smell might simply be it's running too rich at idle. Conditions have likely changed significantly since the fuel distributor was last adjusted. Unfortunately with new plugs and minimal operation since getting it going after all these years, there's not much point in reading the plugs for additional clues. I'm also wondering if unburnt fuel dumped into the system during some of your testing may now be gassing off with a warm exhaust, in which case it may be a short term issue and the smell should soon improve.

I hate to think how many hours so far in refurbishing the tank and fuel delivery system. It's got to be a bit frustrating having it now running again and getting a big stuck chasing the likely last remaining issue.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Thanks for the response. Much appreciated.

I have done a volume test on the fuel pump which is new and it was good. I forget the exact numbers but it was slightly over that suggested by Colin Duncan of kjet specialists in Australia.

The tank is completely refurbished so I have to assume that there is no crud left inside it. All lines were replaced and I have changed out the under hood filter a couple of times to makes sure I am getting the cleanest supply possible.

I will check on the advance of the timing with higher revs, this seems to be something that a lot of folk are suggesting.

I had to rebuild the fuel distributor myself because it was a solid lump of shellac but I followed very strict cleanliness protocols and watched (many) online videos. Used a kit from Colin Duncan at kjet specialists. I have run a test that confirms that all four injectors are getting the same amount of fuel.

I have been wondering about the plunger in the distributor sticking too.

Thanks Brickbopard.

If it idles fine, then it is not far from 100%

Does air metering flap move smoothly? If not, simply take the distribution head off & soak it in gasoline. I would not take it apart.

Don't touch the settings on the CPR either.

I had K-Jet for many years & it worked fine EXCEPT
1: one time it would do nothing but idle & I had to reach in through the air cleaner & lift the flap, it seemed locked, was possibly just some gum or varnish from petrol.
2: Had vapour lock once on a hot day with a low tank of juice. Just filled it up with juice & that was that.

My K-Jet was fitted to a 71 model car, 2130cc, 11.5:1 compression, K cam & big exhaust.

A lot of the basics are covered. My first thought was a plugged cat, but of course there isn't one.

I presume a good strong spark has been confirmed against the block in dim lighting and that the distributor cap/points look okay, also the timing advances okay. Weak coils aren't common, but at that age anything is possible.

I was thinking more along the lines of Phil, fuel starvation and the fuel distributor suffering from gas varnish buildup likely there after sitting for so many years. Easy of course is to start with Phil's advice, checking the plate for easy, smooth movement, a bit of bounce from a high drop, still being centred in the throat and the axle not being worn enough to wiggle side-to-side and able to bind in the throat. My real thought would be deposits in the distributor ports restricting fuel flow and perhaps also needing the mix adjusted to current conditions.

One of our K-Jet experts like Art will likely soon trip over this to add their wisdom. In the meantime, perhaps check out videos on K-Jet fuel distributor rebuild for clues and to see how the guts work. I see a few of those online.

Now if it was only a minor problem I might suggest starting with a high quality fuel injection gas additive to see if that starts to make a difference, but yours isn't really drivable and likely quite beyond such a gradual cleaning.

The K-Jet fuel distributor in my '74 144GL was extremely reliable, only needing adjustment once or twice in its life and twice the injectors needed new seals, but that was at age 15 when I sold it, not 49. Wow, I'm impressed and surprised it hasn't rusted out long ago; Must have been garaged and well taken care of. I did find my city driven engine (with lots of crawling in rush hour) enjoyed a regular high rev Italian tune-up on the highway as well as premium gas and occasional gas additive. Still got a full bottle of that additive hiding somewhere in a box and knowing me at the time, probably a noname brand.

Thinking of other fuel starvation possibilities, you've got good fuel pressure and an easy start, but do consider a worn fuel pump not being able to keep up with demand or fuel delivery being restricted somewhere (other than the filter you replaced). Verify that both the main and in-tank pump are running and the main pump sounds normal. If you're suspicious, you could check timed fuel delivery volume to the engine into a measured jar. There's a spec somewhere. You could also check the amp draw through the main pump after it's been running a bit and become fairly warm. As I recall, 9-10 amps is good and anything close to 14 amps says it's significantly worn and working too hard. I'll also mention that if the in-tank pump had been replaced, it's easy to wire it backwards and cause fuel delivery problems with extremely poor acceleration, hesitation and stumbling like there's a governor. Art maintains it won't run in reverse when wired backwards, but for whatver reason I did have major problems with such symptoms when I once wired it backwards, instantly fixed when wired correctly.

I'm also wondering what the gas tank looks like inside. Gunk or rust flakes could be partially blocking the pickup tube. I believe there's a drain plug on the bottom of your tank. Maybe worth draining a little off to see how bad it is at the bottom.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi,

I have a K-Jet in my 1978 240 GT.
It’s not good for K jets to sit but it sounds like you have cleared the injectors of an issue and have seen normal flow.
The pressures seem good too.

I’ll suggest that you check the air flap inside of the rubber bellows below the throttle as it is supposed to respond to an increase in air flows.
The control pressure regulator holds pressure onto the distributor flap and slots open the volume.

It should only take a very slight breathe of air to lift the plate up.
I would get below the flap with an air hose from up under the intake side by the way of air filter housing cover and it’s duct.
The least amount of air that you can introduce up through there the better it will help check or determine its responses off idle.

The flap needs to be centered in the bore and you have to check that with a mirror and a light if there is a problem.
It is delicate mechanism and do not try to make any adjustments until you know it clean and clear as I see they shouldn’t move on their own from what the factory set.

This flap may be reacting sluggishly or is stuck or even the distributor’s pistons may be sticky from old fuel.
It may need a solvent soaking or flush.
Hopefully you will not need to try a disassembly as that is also a very precisely made unit.

Hope for spider webs or a rodent nest in the intake duct.

Phil