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Old 11-23-2019, 04:01 PM   #1
soclosenotnear
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Default 1994 945 Turbo intermittent no start then start

Good afternoon,

This issue has been happening since I bought this car. Worth mentioning it was a turbobrickers car before me, although I didn't buy it from an enthusiast.

Sometimes, no apparent rhyme or reason, the car will not start. It may have started 6 times earlier that day. Or it may happen on first crank of the day. When this no start occurs, it may or may not actually start on two cylinders for a few seconds and then die. Sometimes it will run on two cylinders (not even registering on the tach) and eventually clear up and run great. Every time, within minutes, it will fire up and run well. I could crank it ten times without it running, then wait ten minutes and it will fire up like nothing happened.

I have a parts car and have thrown the proverbial parts cannon at it for zero cost. But I have replaced cps, coolant temp sensor, o2 sensor, injectors, fpr, cleaned iac valve. I've also converted the car to wasted spark to eliminate the ignition stuff. Swapped both computers. Plugs and wires. Maybe some other things. Nothing has changed my symptoms.

I have no check engine lights. It does not register codes, even when it happens. Otherwise, it runs pretty well for the most part. Last couple times it happened, I've been able to move wiring around under the hood and immediately get it to fire up. The very last time, it cleared up after moving around cps wiring at the connector and nothing else. I pulled the electrical tape back (no rubber grommet?) On the connector and it is two wires and another bare wire surrounding it. It is identical to my parts car and isn't it that bad of shape. So, I thought I found the culprit, but now I'm not sure.

Sorry for the long post, just wanted to get it all out there. Hopefully it makes sense. Am I headed in remotely the right direction? Any suggestions or ideas?
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Old 11-23-2019, 04:05 PM   #2
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It can only ever be the RPM sensor or fuel pump relay. Check both again
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Old 11-23-2019, 04:36 PM   #3
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Check the fuse for the fuel pump, I think fuse #11, I had this happen on my car. I pulled the fuse and the fuse socket had signs of overheating. also check the fuel pump wiring under the car, I hate those bullitt conectors on the fuel pump.
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Old 11-23-2019, 05:08 PM   #4
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+1 for crankshaft/rpm sensor. If while it’s running and you close the hood hard and it shutters a bit, this would confirm that diagnosis. Because of the heat underneath the hood the wires deteriorate over time.
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Old 11-23-2019, 06:18 PM   #5
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Sounds like the crank sensor. Don’t buy a cheap brand, they are crap.
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Old 11-23-2019, 07:38 PM   #6
soclosenotnear
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I'll check out the fuel pump fuse and fuel pump relay as I haven't really looked into those yet.

fwiw, I have already replaced the crank position sensor with a spare that never had an issue.
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Old 11-24-2019, 04:44 PM   #7
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Fuel pump fuses, relay and wiring seem ok. Also jiggling wiring, tapping on the pump didn't help. I do feel like I hear a scratching noise almost coming from the main pump. In the parts bin that came with the car, there are two new spare in tank pumps if that means anything.

Moving crank sensor wiring couldn't get car to start this time in my driveway. After leaving it and coming back, it fired up without issue five times in a row before not starting again.

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Old 11-24-2019, 05:27 PM   #8
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Try reflowing the circuit board on the fuel pump relay even if it it looks good. Just pry the cover off with a flat screwdriver and get some fresh solder on the contacts. They were nice enough not to put any potting on the boards, so you can start soldering right away. Check the ground loops too if nothing else looks wrong. Maybe one of those is what you moved when it cleared up.
Try to do the same thing with the radio suppression relay as the fuel pump relay. It's under the hood and is also not potted, so it may have some corrosion. There is a silicone bead around the cover, but on mine it was cracked apart. In addition to reflowing that one, clean the contacts. Use a spray contact cleaner or eraser if you can, if you want to preserve any remaining plating on the contacts. Beware, the harness side connector may be badly rotted. Mine was. I had to chop off the contacts and splice on some generic 3.5mm bullet connectors with "waterproof" sleeves.

Last edited by iamrolling; 11-24-2019 at 05:34 PM..
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Old 11-24-2019, 06:04 PM   #9
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I'll add to this as I witnessed the 5 times starting perfectly fine, then the next, the car would attempt to fire but would chug maybe once or twice before shutting off.

As soon as the no start happened I started listening the the main inline pump. While it was cranking the main pump is running, confirmed with a length of hose to my ear while he cranked, but like stated, it sounded faintly of a scratching noise along with the normal hum. I personally do not think the relay is the problem if the pump runs while cranking.

The car also reeks of gas after multiple cranks with mo start. A few weeks ago while diagnosing this we pulled the plugs and they were wet and reeked of gas.
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Old 11-24-2019, 06:26 PM   #10
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Originally Posted by Mbeas96 View Post
I'll add to this as I witnessed the 5 times starting perfectly fine, then the next, the car would attempt to fire but would chug maybe once or twice before shutting off.

As soon as the no start happened I started listening the the main inline pump. While it was cranking the main pump is running, confirmed with a length of hose to my ear while he cranked, but like stated, it sounded faintly of a scratching noise along with the normal hum. I personally do not think the relay is the problem if the pump runs while cranking.

The car also reeks of gas after multiple cranks with mo start. A few weeks ago while diagnosing this we pulled the plugs and they were wet and reeked of gas.
I saw somewhere that leaking injector seals can create a strong fuel smell.
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Old 12-09-2019, 01:27 PM   #11
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Got some time to tinker with the car this weekend. My neighbor borrowed a fuel pressure tester from the parts store, so I used it while I had the chance.

Relieving pressure each time
Key turn 1- 8 psi
Key turn 2- 18psi
Key turn 3- 28psi
Key turn 4- 36psi
Key turns 5-8 - 40ish psi
Running 35-36psi and with any throttle got it to 44-45psi

So, with a spare in tank pump on hand we swapped it out. After getting the old pump out, we discovered the filter screen was torn open and the pump would not power on with direct 12v applied. I thought I found my culprit.

So today, took it to run errands and am now writing this from a parking lot while the car won't start. Still really leaning towards fuel delivery issue.

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Old 12-10-2019, 02:46 PM   #12
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For grins and giggles

Can anyone speculate on what my fuel pressure readings could mean? Should it build full pressure on key turn number one?
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Old 12-11-2019, 07:57 PM   #13
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I'm pretty sure it should build and hold 38 psi when you first turn the key and then stop until you start the car, by the way I'm having the same problem as you right now very frustrating.

Pull fuse #1 and check/clean the contacts on the fuse. I just ordered new bullitt connectors for the fuel pump from Dave Barton. I'm running out of ideas.


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For grins and giggles

Can anyone speculate on what my fuel pressure readings could mean? Should it build full pressure on key turn number one?

Last edited by Dicktater; 12-11-2019 at 08:03 PM..
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Old 12-12-2019, 10:31 AM   #14
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Originally Posted by Dicktater View Post
I'm pretty sure it should build and hold 38 psi when you first turn the key and then stop until you start the car, by the way I'm having the same problem as you right now very frustrating.

Pull fuse #1 and check/clean the contacts on the fuse. I just ordered new bullitt connectors for the fuel pump from Dave Barton. I'm running out of ideas.
Thanks for the response and yeah, it's a real bummer. I've pulled the fuel pump relay and fuses and cleaned them but they looked fine. I saw in another thread something about a fuel pump check valve but I think the car should eventually start if that fails. After having my car towed home, it still wouldn't start. Two hours later, it fired up on the first key turn, ran rough and then smoothed out perfectly. I need to get the fuel pressure tester back and see what it does with the new in tank pump.
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Old 12-18-2019, 07:49 AM   #15
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Did you say your FPR (BOSCH 3.0 bar) is new?

Would be interesting to carry a spare plug, and when these NO START events occur, pull a wire and lay your spare plug on a nice ground..... crank and test.

Spark or fuel, yes sir.
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Old 12-18-2019, 06:57 PM   #16
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I found my problem.................Finally.









The wiring for the main pump is way undersized, I bought these from Dave Barton....what a great asset to old Volvo owners...........Thanks Dave!!


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Old 02-07-2020, 04:02 PM   #17
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I just wanted to update this with my solution.

I ended up buying a new crank sensor that didn't help my problem. My brother and I fairly extensively tested the coolant temp sensor and confirmed it was working at all temperatures per Volvo spec. Eventually we realized when the no start was happening, we could induce it to fire up by unplugging 1 or 2 injectors. It was flooding.

Long story short, after revisiting the fuel system, I swapped the original (afaik) -967 lh2.4 box for a spare -984 box. Since swapping computers, the car has started every time. No rough starting and then smoothing out at all. I'm about three weeks in and countless starts without problems, so I believe the issue all along was this bum fuel computer.
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Old 02-07-2020, 04:06 PM   #18
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Congrats on the repair, It sucks not to be able to trust your car.
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Old 02-07-2020, 04:08 PM   #19
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Try plugging the old computer back in to see if was the computer or possibly just some fretting on the terminals.
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