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In early 2020 I started looking after a modest car collection for a gentleman who owns (among other things) a '88 951 with nearly 80k miles. Later that year the turbo gave all it had to give so I had an indy remove it and send it out for rebuilding. While they were there I asked them to do the timing belt and water pump, as the owner of the car didn't have any records for it. Upon collecting the car everything seemed to be in order and it ran fine.
In January 2021 I found a leaky fuel injector. Shortly thereafter I removed all four injectors and sent them out for cleaning and calibration. Upon receipt of the injectors the company carried out testing and found them to be in quite a state. After cleaning and calibration they were said to be in excellent nick, as one would expect. I installed the injectors in March and, again, everything seemed to be in order and the car ran fine.
August rolled around and the car wouldn't start. Only 30 miles had been covered by this time as the owner doesn't drive the cars often. I tested the coil, it checked out fine, and the car started despite having done nothing else to it. A month passed, the car covered no miles, and it wouldn't start again.
I started searching online and got some hits on Pelican Parts and this forum, which lead me to spending time on Clark's Garage (RIP).
This forum lead me to the the crankshaft position sensors, or the speed and reference sensors or whatever they're called. I replaced those in October. It didn't start.
Clark lead me to the distributor cap and rotor. I replaced those in November. It didn't start.
This site lead me to the fuel pump check valve. I replaced that last month. It didn't start.
Pelican and Clark lead me to fuel pressure testing. Last month, after jumping the fuel pump relay, I observed 2.6 bar fuel pressure at the end of the rail. I then tried starting the car and it lit up! It ran very poorly and white smoke poured out of the exhaust. I shut it off.
Also last month I did the leakdown test described on Clark's site. Starting with 2.6 bar, it dropped to 2.4 bar after four minutes, 2.2 bar after 11 minutes and 2 bar after 21 minutes. Apparently it did exactly what it was supposed to do per Clark's site. With the engine running (poorly) I observed 2.5 bar, which is high according to Clark.
Since I don't have an assistant to ground a spark plug against something in the engine bay I checked for spark using a light installed between the plug and the cap and all four plugs are, well, sparking. The car never starts unless I 'prime' the system by jumping the fuel pump relay for a few seconds.
In case it's not obvious, I know about enough to be dangerous. And while I'm not a terribly good mechanic I'm not afraid to get stuck in and have a go. Thing is, I'm about out of ideas. Short of installing a new fuel filter or maybe a fuel pressure regulator I don't know what's left to do.
All of my efforts have been focused on fuel and ignition thus far. Is there somewhere else I should be spending time? I just can't seem to move away from that area because the fact it starts with a bit of trickery makes me think that it is indeed a fuel delivery issue.
It's been three years and 16 days since I logged on to this site. I hope you won't hold that against me. Thank you in advance.
Thank you for the input, Dan. Indeed I did not replace the fuel pump relay. In fact, I haven’t hardly given it a second look. I’ll pull it tomorrow and see what I can see. Thank you for the photos!
Check DME relay for sure. You can bypass the relay by rigging three small wires and spades to connect into the sockets. Plenty of posts describing this process. If it is a bad relay, the bypass process will start the car. You will hear the fuel pump kick in.
if that’s not the issue then I would send the actual DME or ECU (the computer) to ECU Doctors for testing. They also repair ECUs for reasonable price.
Here's the DME. Looks pretty good to me. There's a little 'gunge' around those lower contacts, but no hairline cracks that I can see. There is a piece that looks slightly bent but, again, I don't see any cracks associated with it.
Can you check the timing? Also a good ideea would be to clean the grounds near the speed sensors ( one on the block and one on the bell housing) and also the ground from the battery to body. also if the gas it's older than 6 months it would be a good ideea to change it with fresh gas.when you crank the car does the tacho bounce?
@alex_cristocea Regarding timing, lately the car won’t run long enough to get out of the driver’s seat and into the engine bay, but I will try next week when I see the car again. As for the speed sensor grounds, I cleaned those when I installed new ones last October.
By now the gas in the tank is probably older than six months. Considering the effect modern gas has on my carbureted motorcycles I like the idea of swapping for fresh. Making that happen, though, will be tough given the car is effectively immobile and where it is parked isn’t conducive to draining fuel.
@944M3 Excellent link. Thank you. I will make one of those next week and try it on.
Dont mess around with the old DME relay … do yourself a HUGE favor and get a new relay from Focus 9 .. not only is it new tech but you can order it with the additional LED lights that will tell you” At a glance” what circuit is not functioning properly. They also offer a “ priming” function.
However, this is looking more like a deeper issue or a combination of issues. I humbly recommend performing a step-by-step diagnosis a la official workshop manual. A good place to start is at the ECU / DME computer located behind where the passenger's feet rest. One of the two boxes is the ECU / DME. If you can pull that out, you can unplug the big socket thing and do all kinds of tests with a voltmeter. Note that this is for an NA not 951--a couple of these values are different, but not many. Ex: on 951, full throttle switch should be no continuity fully open
If most of these prove good, then you can go through all the steps in the official diagnostic procedure:
Symptoms are white smoke when actually running and it does run when dme jumped. Why would you pull the computers and break out a meter and or a scope? Only use oem bosh pickups, if they are aftermarket toss them.. i think everyone would agree on that point.
pressurize the cooling system with a tester.. look down the holes to see if water is getting in… dme relays are very temperamental.. i was qualifying my race car last fall in west virginia… got two laps and the car just shut off like i hit the key… had to do the “ tow of shame”.. then the car ran again… switched the dme no further issues.. again the focus 9 has self- diagnostics built in…
I'm confused: I thought "...the car won’t run long enough to get out of the driver’s seat and into the engine bay"? Is this after jumping the DME relay or not?
02-24-2022, 01:05 PM
'88 951 Won't Run
