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Discussion Starter · #1 ·
so i've been bringing this '74 volvo 144 back to life...

she runs GREAT at high speeds, but has a REALLY ROUGH idle, just stumbles when in Park, and almost dies when you put her in gear.

i've checked the cold start injector and the thermal time switch, and both seem to be fine. the air filter's not too bad, and the inline fuel filter is new, at least. (i'm working on replacing the in-tank filter as well.)
she starts really pretty well when cold, but seems to be a little harder to start when warm (though it may just be my imagination).

anybody want to hazard a guess at the most likely culprits?
are we guessing that the injectors are leaking? something else?
 

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Re: ROUGH idle in my fuel injected '74 (pelos)

Try spraying carb cleaner around the fuel injectors at idle. If the engine picks up speed, the seals around the injectors are bad. There is an O ring between the aluminum holder and the head and seals around the injector and holder. You have to readust the idle screw after they are replaced.

Is this an EFI or CIS car?
 

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Re: ROUGH idle in my fuel injected '74 (VolvoBob)

bob, it's so great hearing from you.

it's a CIS.

this afternoon, i tried spraying wd-40 (maybe that was a bad idea, but for some reason, i was afraid that carb cleaner might damage the rubber/plastic components?) and didn't notice any change. (except that wd-40 started smokin'
))

i'm not really familiar with this stuff (i've owned carbureted vehicles for a long time)...don't really know what to try next. should i try the carb cleaner, or move on to something else?

should i just go ahead and replace the seals for good measure? (it looks like they're available for about $6/each). or is that a big job that may not need to be untertaken?

do we eliminate the fuel distributor, line pressure regulator, control pressure, auxiliary air valve and whatnot because she runs so good when not at idle, or ? and what's this little electronic switch thingy directly underneath the idle speed adjusting screw?

any other tests/ideas?
 

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Re: ROUGH idle in my fuel injected '74 (pelos)

Lee,

I'm relying on some dim memories here, the last K-Jet car I worked on was an Audi 5000 about 14 years ago.

What you're describing sounds like it could be a few different things; if the AAV isn't operating properly, that may be it... if it isn't getting voltage, it'll lean (or rich? ...can't remember) the idle mix too much. Same if the spring's broken. Test for the valve: Hold it to a strong light, apply 12V briefly, see if the light level through the hose fittings changes. Also check for the valve getting voltage when it shouldn't... same result in engine performance.

Bosch CIS is heavily dependent on the injectors properly atomizing the fuel; use the 'mayonnaise jar test'. Pop an injector out, put it in a large glass jar, have a helper crank the engine a bit, and watch the spray pattern. It should be a mist; if there's more than a hint of a stream, resign yourself to replacing the injector. At higher RPM's, this just results in poorer combustion. At low RPM's, it 'simulates' the wrong air/fuel ratio.

There is also an idle air by-pass adjustment (at least on the Audi)... it's either in or near the fuel distributor, if memory serves. I could be wrong.

Also, get the engine warmed up to operating temperature, and dismount the cold start injector (We're going 'mayonnaise jar' again). Leave its electric and fuel connections intact, and ground it to its normal ground point... it may appear fine, and test OK, but if it's even partially energized (bad ground, sender, or wiring likely) it *will* leak, thus unnaturally enriching the idle mixture. Again, not apparent at higher RPM's.

Any disturbing of the air plumbing upstream of the fuel distributor can also wreak havoc...

Oh, and by the way, you have my sympathy
I'm not real fond of K-Jet. Whatever you do, DON'T disassemble the fuel distributor!

-Chris.

Modified by Alaric at 5:21 AM 6-22-2006
 

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Discussion Starter · #5 ·
Re: ROUGH idle in my fuel injected '74 (Alaric)

chris- thanks so much for the input.

the aux air valve seems to be functioning. voltage is getting to it, and it looks to have been replaced recently, probably by the previous owner. with the engine "cold" i checked it with a flashlight and mirror, and the valve appeared about 1/4 open. after starting the engine and letting it run for a minute, i killed it and rechecked, and the valve was open a much smaller crack...does that sound good to you?

i checked the cold start unit as you suggested, and it appears to be pretty new and isn't leaking.

not aware of an idle/air bypass, and feel darned confident now that there's no leaks in the air hoses. HOWEVER, i hear a little hiss i think coming from where the A/C idle solenoid screws into the idle speed adjustment screw/assembly. the solenoid has a threaded metallic base, and screws into the idle speed adjustment assembly, but won't "tighten down" on it fully, and can be turned by hand with some pressure. think this is a problem? recommend a fix? don't know if it helps diagnostics, but the car will seem to be idling somewhat decently in park, and then will die or stumble badly when put in gear.

i've considered taking the fuel distribution unit off of the air control unit and cleaning the air unit out, replacing the Oring and gasket even though i can't get them to show signs of leakage when spraying them w/ carb cleaner. do you recommend against this disassembly, or just the dissassembly of the fuel distributor/line pressure regulator itself?

Modified by pelos at 4:42 PM 6-23-2006
 

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Re: ROUGH idle in my fuel injected '74 (pelos)

Lee,

You're OK working on most of the fuel distributor; just don't crack it open (this is a machined fit with no gasket. Nobody I know of could ever get it to seal properly again... and this includes me
). Make sure the cold start injector is getting NO voltage after the engine's been running for more than a minute or two (could be a bad thermal timer). I'd still look at the injectors first.

N.B.: The thermal timer's a device that screws into the water jacket. It supplies cold-start voltage for about 90 sec. to 2 min. It's in the water jacket so that it can override the timer function for a warm start. Be grateful you don't kave KE-Jetronic! (I think Volvo called it 'Lambda-Sond' or some such)

Before delving too deeply into the fuel system, be sure of your fundamentals as well... proper ignition timing, etc.
 

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Re: ROUGH idle in my fuel injected '74 (pelos)

Lee,

After consulting with my best friend (the former owner of the above-mentioned Audi 5000, and an ASE-certified mechanic [which I am not]), he mentioned one huge overlooked trouble spot on older K-Jetronic cars; check your brake booster! It can create just the trouble you describe if it's bad, and the check is very simple (if hard on the legs)... disconnect the booster hose on the engine side, cap the connection, drive the car as usual, and see if the problem goes away.

Be aware that brake pedal effort will be a lot higher.

Apparently, the check valve in the brake booster (cheap) and the brake booster's diaphragm (not so cheap) go out more often than I might have thought. In the same vein, you might check other high-vacuum accessories like the distributor advance can, vacuum modulator (if you have an automatic transmission) and (if applicable... can't remember...pretty sure your controls use cables, not vacuum) heater controls that can be big but not obvious vacuum leaks. Use a hand vacuum pump on the heater and distributor and watch the guage to be sure that they either hold vacuum or 'leak-down' within the factory-specified time limits. Check your Haynes, Bentley, or (ugh) Chilton manual to see what those limits might be.

He also mentioned a device which lowered fuel pressure when the engine was warm, and that might act up, but that device may or may not be on your Volvo. Might have just been an Audi thing, although K-Jetronic tended to vary very little between engine applications.

Incidentally, the air filter kits for the brake booster were available as recently as a year ago, when I bought one from Fisher Volvo... if memory serves, the recommended replacement interval is every 3 years. To my knowledge, not one has ever been replaced


Modified by Alaric at 5:47 AM 7-8-2006

Modified by Alaric at 5:50 AM 7-8-2006
 

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Discussion Starter · #8 ·
Re: ROUGH idle in my fuel injected '74 (Alaric)

WELL!
i've tried a bunch of the suggestions, and i guess we're narrowing it down but the problem continues. lemme run it down for ya:

1. brake booster check valve checked out okay, and plugging the booster vacuum lines had no effect on idle.
2. i don't have vacuum advance for the distributor....centrifugal only, so i'm guessing that's not an issue.
3. i do have a automatic transmission, but i'm not familiar with the location of the vacuum modulator, and it's not in my book, so i'm unsure about how to test for it. when slowing down to a stop, i do notice a "clunk" in the transmission, and have hoped that it's a result of the engine starting to idle poorly / rev and is "tricking" the transmission somehow...
4. the car usually has a hard time starting now. it will try to fire, or fire and then die, then eventually crank up, is uneffected by warm or cold engine, and the plugs aren't blackened and there's no smell of gas.
5. The fuel pump relay's contacts look clean and non-corroded, but i'm unsure how to test the relay itself. the fuel pump fuse and it's contacts look good as well.
6. it still idles poorly, and tries to die when it's put in Reverse or Drive.
7. i pulled out two of the injectors and cranked the motor while watching them, and they instantaneously spray a little misty pattern, but i wouldn't call it a pure, symmetrical, complete mist. the injector sides and seals are oily and dirty, though not sure if this effects anything as tips themselves look clean?
8. i took the air cleaner and air control unit off, replaced the o-ring on the sensor and sprayed/cleaned the residue off the whole thing with carb cleaner and reinstalled it all with a new k+n filter and a new gasket between the fuel distributor and control unit. didn't seem to change anything.
9. i've tested the cold start injector several times. it sprays when for a couple seconds and then stops, and doesn't leak.

any suggestions?
replace the injectors? find a way to test the fuel pump or regulator? anything?
 
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