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Old 05-09-2021, 08:23 PM   #1
bionicbanana
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Default Another Intermittent No-Start Thread

93 940 Turbo



Had a cold morning a few weeks ago and car wouldn't run for more than half a second, sputtering badly. Eventually fired up and ran great for a week or two with no issues (aside from a blown turbo, burning a lot of oil under normal driving). Replaced the turbo with another 13c I had lying around and drove fine until the next day, when the problem occurred once again when cold, and again after starting it back up warm, basically limping it to a friend's place up the road travelling 2 miles an hour in 1st

Since then the issue has stuck around and the car has been basically undriveable. Disconnecting the battery for an hour+ seems to do the trick until it's turned off and started again. Here's a list of things I went through already, some of which not seemingly related:

Cleaned MAF and connection. Had the battery disconnected during this time and it started fine after, good ground and 2.5v between pin1 and pin3 at idle.
Swapped with another known working MAF, no change
Two different coils, tested working, no change
New plugs + boots cleaned. Spark on all 4 when cranking
IAC + connector cleaned
Air Filter cleaned
Tried another radio suppression relay, no change
CPS connector cleaned and replaced sensor, no change
02 sensor + connectors cleaned, swapped a new bosch one in too, no change
Ignition + cam timing verified
All visible engine grounds and battery terminals cleaned and tested
Not getting diagnostic codes, only 1-1-1
Swapped fuel pump relays, both pumps priming with key turned
Swapped power stages, no change
Cleaned ECT connection, not tested
Cleaned TPS connector, ran diagnostics which tested okay
All fuses checked and replaced
Ignition switch replaced, no change

Most recent was swapping the MAF, and once again it started up and drove great after having the battery unplugged for a bit. Got back from the drive and wouldn't restart.

I suspected it was a charging issue since I wasn't always getting dash lights with key turned, though that's been a reoccurring problem over the past few months (neglected). It would however drive fine with working speedo/odo even without warning lamps on with key turned up until recently. Today the cluster was pulled and we basically just fiddled with connections and now I'm getting lights again, with 12v at the exciter wire at alternator.

Not sure where to go from here. I could be wrong, but it seems to not be a fuel or mechanical issue given the intermittency of the issue, and the fact that a battery reset seems to work.

Another thing to note - the ignition switch/starter is sticking a bit, and still cranks for a second when key is turned back to ON. It's been doing this for a few months though. I assume that much more fuel is being sprayed by the injectors while cranking vs idling. Is it possible the problem has worsened and now it's flooding itself?

Any help is appreciated. Thanks

Last edited by bionicbanana; 07-25-2021 at 12:21 PM..
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Old 05-09-2021, 10:06 PM   #2
ZVOLV
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Got a test lamp?
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Old 05-11-2021, 08:56 AM   #3
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Got a test lamp?

Should somewhere. Been using a multi to test everything else
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Old 05-11-2021, 10:37 AM   #4
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Should somewhere. Been using a multi to test everything else
A meter is the wrong tool for testing power circuits. I've been informally, and formally, trained on this.


Test lamp from coil NEGATIVE to ground. Key on, illuminate? Crank, blink? = (ignition pulse)


Peel back the boot on an injector connector, unplug the connector, crank, BLINK? =fuel injector pulse.

I bet its your crank sensor, or possibly the "injector" relay (aka radio interference relay)
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Old 07-18-2021, 01:52 PM   #5
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What is the negative on the coil? And where am I hooking up to on the injector plug?

Tried new CPS, Radio suppression relay, and ignition switch. Still same issue - starts up and drives great after battery has been unplugged for a while. Try to restart after parking and stumbles upon starting and dies

EDIT: Figured it out and yes, solid light from coil when key is ON and blinks when cranking. Still unsure where to test on injector plug

Last edited by bionicbanana; 07-18-2021 at 02:02 PM..
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Old 07-24-2021, 04:05 PM   #6
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Alright I'm about to crush this ****ing car...

Any other ideas? I really need this to run as it's my daily. No shops in town really work on volvos and the cheapest is 90/hour so that's not really an option. Have tried everything except swapping a different ecu.

Still the only thing that works is disconnecting the battery for a day. Leaving it connected but not touching it for days doesn't work...
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Old 07-24-2021, 05:06 PM   #7
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How's your fuel pressure?
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Old 07-24-2021, 05:40 PM   #8
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This will be an easy fix.

No need to get rid of the car because of an electrical problem that someone with experience will know how to diagnose.

Whenever something goes wrong on these old classics, 9 times out of 10 it's an electrical connection
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Old 07-24-2021, 07:25 PM   #9
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Ok so it runs, but it runs like ****?

You could have a massive air leak or barely any fuel pressure.

Pull the codes with the OBD blinky thing.
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Old 07-24-2021, 08:11 PM   #10
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Ok so it runs, but it runs like ****?

You could have a massive air leak or barely any fuel pressure.

Pull the codes with the OBD blinky thing.
Like I said, runs and drives perfect after having the battery disconnected overnight. Once I turn the car off, it will barely fire up and die after half a second. I can drive it for an hour or 10 seconds, doesnt make any difference. No CEL, no codes given when I use the diagnostic plugs under the hood. Good fuel pressure at the rail, has spark, obviously no vacuum leaks or bad gas considering it runs perfect with a reset. Tried multiple cps and radio relays, fp relays, etc.
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Old 07-24-2021, 08:51 PM   #11
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What is the fuel pressure? You can't just say " I have pressure at the rail."
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Old 07-24-2021, 10:19 PM   #12
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Quote:
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What is the fuel pressure? You can't just say " I have pressure at the rail."
~40 at the fuel rail
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Old 07-25-2021, 12:29 AM   #13
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What's the O2 voltage when the issue is present?
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Old 07-25-2021, 12:40 AM   #14
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Quote:
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What's the O2 voltage when the issue is present?
Will check tomorrow. I had a spare I tossed in today without any change but will test it
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Old 07-25-2021, 01:07 AM   #15
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You may find it pegged lean at 0.1V or pegged rich at 0.9V. Check after engine has run for several minutes.

The ECM sounds suspect.
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Old 07-25-2021, 01:58 PM   #16
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With the problem you are experiencing I would be testing the ECT output when the car is cold and warmed up. Just check for the ohm readings at the ECU connector.
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Old 07-31-2021, 11:08 AM   #17
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Quote:
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With the problem you are experiencing I would be testing the ECT output when the car is cold and warmed up. Just check for the ohm readings at the ECU connector.
Which pin on the ecu is it? I will check today. I suspected that as my valve cover was leaking a bit on that side and tried 2 spares without any change. Cleaned the connector as well.
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Old 08-04-2021, 07:54 PM   #18
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I had an issue like this when my iac was starting to go bad. Tried cleaning it and still had the issues eventually replaced it. The new one actually slipped at a crooked angle and again showed similar issues. I put it upright and secure and it fixed my issue. Maybe not something related but maybe see if it starts the same way with the iac unplugged? Don’t know if that would be a good test but I’m sure the guys on here know.
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