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My 1994 945T cranks strongly, has spark, fuel at the rail, correct timing, but will not start. It gets 12v at the injectors, but neither noid light nor test light flashed on cranking. Swapped fuel relay and RSR, nothing. I swapped ECUs but no positive change - strangely the cooling fan came on as soon as it was plugged in (no key). I’ve run DTM 3 and could hear the injectors clicking. No codes. No start with starting fluid. The ballast resistor wiring seems a little hinky, I resoldered some of it - could that be causing a starting problem even though I get battery voltage at the injectors?
Some background: about two weeks before this happened, I replaced the rear seal. She started and ran fine for maybe a week, then slightly sluggish acceleration for a few days, then was not able to start one afternoon trying to head back to work. Could I have screwed something up that would take a week to show itself?
Additional background: two years ago she was hit at the driver’s front corner, and while being repaired required a bit of rewiring up there which was carried out by some jackleg with an electrical tape fetish who forgot to attach BOTH the ABS and the cooling fan wires. Started and ran fine until now, though…
I suppose the next step is to thoroughly check all the wiring involved. I have to a certain extent with diagrams and a multimeter but so far nothing seems amiss - what’s the best path forward at this point? Truly grateful for any help or suggestions!
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This afternoon I installed a new battery, plugs, coil, and ignition amplifier - wanted the best possible spark now that I had fuel in the cylinders - and she fired right up, runs pretty well. Now to replace all the parts I stole from her poor sister...
While I had the plugs out I did a compression test. 120/135/135/90. Wet test brought the 90 up to 120, so maybe new rings soon?
Thanks for your suggestions and guidance. Sites like this are vital for maintaining and enjoying "older" cars.
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So the wrong ECU was at the bottom of all the misery?
Did that car sit for months unused?
Does it burn a lot of oil?
Try a long soak of mystery oil.
A day or so soak might free up a stuck ring and maybe
surprise you with better compression test results?
Maybe all that cranking without ignition damaged the engine?
Volvo says to disable the fuel when doing compression tests
so you dont wash out the oil from the cylinders.
Bill
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No, the ECU swap was just a test. When no positive changes occurred I removed it and set it aside. The original unit was fine apparently.
She was a daily driver, and more of a leaker than a burner. The new rear seal has hopefully stopped that. Should the mystery oil go in the cylinder itself or just in with the oil, or does it matter? What about Restore? I've read some good things but???
The car wasn't cranked too much, and I took out the fuel fuses for the compression test.
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This has worked for me before with a stuck oil ring.
Put a teaspoon or so of MMO in each cylinder and let it soak a day or more.
Get newspapers or paper towels and crank a few times with the plugs out to
help clear it away before starting the engine.
Then see if you get lucky with better compression test numbers.
Are you using full synthetic motor oil?
Report back, Bill
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Got lucky, it seemed to work! Put 2 Pipettes of MMO in each cylinder two evenings in a row, jiggling the crank a little each time, and then let sit another night. Spit it out, replaced the plugs, and took her for a drive.
Warm compression test results: 155/165/165/155
Previous (cold) results: 90/135/135/120
Forgot to open the throttle for the test (oops), but still, what a positive change! Did a cold test the next day and got similar numbers. Thanks, Bill, for that great suggestion! And yes I am using synthetic.
The car started running kind of rough, popping/missing and eventually stalling. Very hard to start and keep running. Put in a new rotor, a better distributor cap, and let her have the plug wires from her sister. Started and ran well. I'll soon get some Bougicords and a new cap. Are the OEM F wires worth the extra 30 bucks?
Still more than a few things to do for her (some fun and some not as fun) but every bit of that work is worth it. Thanks for everyone's help!
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That's good news.
MMO works on stuck rings.
Are you using a synthetic blend or full synthetic. What specific oil?
You didn't say if your car sat for a long time unused, that might account for stuck rings.
Those symptoms of the engine running rough and stalling without applying gas
are what I inherited as a chronic unsoloved problem in my 940.
I replaced the fuel relay and cleaned and put new thermal paste on the ignition
module.
The engine has not hiccuped since last summer, so I'm almost ready to declare it's fixed.
Avoid cheap plug wire sets, do use dielectric silicone on the top of the plugs,
and maybe using plug boot pliers is a good idea.
I'd like Brickboard comments on plug boot pliers, are they worth it?
Cheers, Bill
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Got lucky, it seemed to work! Put 2 Pipettes of MMO in each cylinder two evenings in a row, jiggling the crank a little each time, and then let sit another night. Spit it out, replaced the plugs, and took her for a drive.
Warm compression test results: 155/165/165/155
Previous (cold) results: 90/135/135/120
Forgot to open the throttle for the test (oops), but still, what a positive change! Did a cold test the next day and got similar numbers. Thanks, Bill, for that great suggestion! And yes I am using synthetic.
The car started running kind of rough, popping/missing and eventually stalling. Very hard to start and keep running. Put in a new rotor, a better distributor cap, and let her have the plug wires from her sister. Started and ran well. I'll soon get some Bougicords and a new cap. Are the OEM F wires worth the extra 30 bucks?
Still more than a few things to do for her (some fun and some not as fun) but every bit of that work is worth it. Thanks for everyone's help!
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Installed a better ballast resistor from the pnp (out of an 89 760, no less) and a new CPS (it had been promised to the other car). Cranks and wants to start, sputters a little, but only when the key is in "start." There IS now fuel in the cylinders, however, so progress is being made...
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You never said if it starts with the AMM unplugged?
Did the ECU's changed have the same part numbers?
You might measure the current draw of Fuses 1 and 11
and see if the fuel relay (and ICU controller) is behaving.
See here for the nifty HF unit that measures current in a fused circuit:
https://www.brickboard.com/RWD/volvo/1685010/940/960/980/V90/S90/review_harbor_freight_30a_fuse_circuit_tester_67724.html
or use your VOM to measure DC millivolts across the top legs of the
ATC fuses 1 & 11
and derive current draw from the chart:
the complete chart is here:
https://m.roadkillcustoms.com/wp-content/technical-pdf/Standard%20ATC%20Fuse%20Voltage%20Drop%20Chart.pdf
Happy hunting, Bill
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AMM unplugged never made any difference. The ECUs were different numbers, 967 vs 560, but the FAQ seemed to imply a certain amount of interchangeability. I guess not. That Harbor Freight tester does look nifty and, as usual, the price is right! Thanks, Bill!
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Crank and Spark means your CPS is working. 12V on the injectors sounds like the RSR/Injector Relay is working.
That goofy ballast wiring could have shot your ECU's grounding circuit for the injectors, but if the injectors click (does your car have a cold start injector?) then it should be fine.
Very strange that your cooling fan comes on immediately - Is your car the type with an electric main cooling fan and the huge relay that controls 2 fans, or do you have the pair of identical relays that you can swap between the Aux AC fan and the RSR?
You could always add on some extra ground wires. I have a feeling that something very odd is going on here.
I would also look at the firewall and look for lack of grommets. Wire insulation could have worn away and shorted on the firewall passthroughs since then. It could also be something infuriating like a slightly pulled apart connector.
Good luck... I hate to say it, but this might be tough. Hopefully it's easy though!
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Thanks for the response. It's got the big relay, swapped it with the one from my other 940, fan still runs with that particular ECU installed.
I was thinking about replacing ECU ground wires and running a new wire from ECU 18 to injectors if only to see what happens.
It's been tough already, don't wanna take it in, I hate to admit defeat!
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To be fair, you're probably the only one who has a shot at figuring this out.
If the injectors pulse in test mode, then they work fine. Wiring and ground should be ok. I asked about the CSI (cold start injector) because it may be the only thing clicking on its own. Put your hand on the injectors and see if you can feel the click.
If the fan relay is coming on instantly... in kp2 or engine off? With the AC set on max, I think it may run the fan any time the key is on. Hopefully that is a red herring. If not maybe you have grounding issues between engine head and body and/or block, a blown fuse or burned/cut wire.
Don't give up on it. I had this weird injector pulse stalling only at certain road speeds (steady engine position) issue that turned out to be 1 wire from the tps coming loose and grounding out on the hot EGR but only when the engine eas tilted exactly the right amount - right at 55mph lol.
I also had this issue where I suddenly got a no-start 500 miles after puling thr cluster. I had picked the wrong wire to hook to my tach input, but it worked long enough for me to make it 500 miles from home!
And other seemingly unrelated work done recently?
William
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OK on +12VDC at the injectors, now you need to confirm that the ECU is grounding
the injectors to complete the circuit.
Check for broken/missing ground wires to the intake manifold.
Another culprit might be a bad CPS.
Bill
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Thanks for replying. The intake manifold grounds seem intact, cleaned them up a little, continuity is there. CPS should be ok, as she's getting spark.
How should I check for injector grounding? The noid light results seem to indicate none, but how best to determine wire/ground integrity? Between ECU 18 and injectors I've found continuity, and the ohmmeter results don't seem to show anything wrong. Maybe run a new wire as a test?
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Another possibility...
See if it starts with the AMM unplugged.
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