No start, no fuel

alpinewhite · 10:51 PM

Hi all,

We have a 1983 944 that sat for 15 yrs and we're trying to get her fired up again. Here are some data points:

- We have replaced: fuel, fuel pump, fuel filter, RPM sensor, battery, oil, fuel pump relay, starter.
- We have spark. Car would start on ether but won't stay running.
- fuel pump turns on only if we jump fuse 2 and fuse 3
- fuel pressure is present at injector rail. We know so because fuel squirts out strongly when we remove the cap at the end of the fuel rail.
- we cleaned the fuel injectors by pulling them out and pressurizing one side and cycling voltage through the solenoid and seeing that we have nice spray patterns.

The only remaining thing we're not sure of is whether the fuel injectors are getting pulses from the DME. I googled and saw that there are automotive multimeters (e.g. Fluke 88v) that'll measure pulse duration. If we put one of these meters to work, it'll tell us if the injectors are, indeed, getting pulses from the DME.

Is there another way I can test for pulses? If the DME is not sending pulses, what could be the culprit? The DME doesn't appear to be totally dead as there is spark.

Thanks in advance.

mytrplseven · mytrplseven's Garage

Two things I can suggest right off: turn the starter and see if the tach bounces about 1/16th inch. It's barely perceptible. If it doesn't, I look at the speed and/or ref sensor. I just had identical issue and it was the speed sensor (closest to the firewall). There's a round shim under this sensor that's held on with the bolt and if it's missing, the sensor will drag on the teeth of the flywheel and damage the new sensor. That's what the problem was with my car. Clarks garage has a good article on checking the resistance of each sensor to verify failure status and how to remove them. Second (and easier) is to get a new DME relay (They're about $20 to $25 on line). Buy two so you always have a spare. Don't get the Uro ones. They fail about 1/2 the time when new. Get some other mfr or go to Pelican Parts. If you're unsure if the injectors are being pulsed, get a noid light at the auto parts store. They're real cheap and work great. Pull the injector connector on each injector (be careful you don't lose the spring clip) and plug the noid light into the connector and start turning the engine. The light will flash each time the injector is pulsed. Good luck with the adventure. Drop a line here when you finally find out what the problem was or to confer further.

SolReaver · 10-24-2015, 07:00 PM

+1 on the noid. Bosch type. Some auto parts stores loan them. Pretty cheap. Check connections and continuity on your speed and ref sensors. Clean ALL grounds.

alpinewhite · 08:35 AM

The fact that I have spark means that I have a good speed sensor and reference sensor, right?

sausagehacker · sausagehacker's Garage

Quote:

Originally Posted by alpinewhite

The fact that I have spark means that I have a good speed sensor and reference sensor, right?

Generally, because the DME controls the spark timing as well.

Maybe the DME itself is bad?

Another thing you can do is pull back the boots on the injector connectors and inspect the wiring for shorts or bad connections into the clips.

alpinewhite · 10-25-2015, 06:43 PM

Based on the schematic I found on:

http://www.pelicanparts.com/944/electrical/944_84_1_2.jpg

the first part of the fuel pump relay (pin 2 to pin 8) provides power to the fuel injectors. The jumper I put from fuse 2 to fuse 3 only bypasses the 2nd part of the relay (pin 2 to pin 4). This is making me believe that the first half of the relay (pin 3 to 1 and pin 2 to 8) is what's bad.

I just ordered a pair of these relays. Thanks for all your help. I'll keep you posted if I get it started.

Oh and I also ordered my noid lights. That'll be useful for future debug.

alpinewhite · 03:00 PM

Today, I replaced the fuel pump relay. The old one bench-tested fine, though, but I thought I'd put the new one anyway. Yes, I bench-tested the new one first (one of the two I ordered from AMZN didn't work right out of the box. I didn't get the URO parts per this forum's recommendation).

At first, she wouldn't start so I got the noid lights out. I confirmed that I get pulses to all 4 cylinders. Then, I yanked out the injectors along with the injector rail. we put 4 cups under the injectors and saw that no fuel squirts out when cranking. We put voltage directly to the injectors and saw that fuel squirted out so we confirmed that we have fuel pressure. I thought that maybe the DME wasn't giving enough voltage difference across the injectors.

We put everything back on and were gonna call it a day. Then, we thought we'd try to start it again with ether. We noticed that we needed less and less ether to make it idle until we eventually were able to keep her idling. SHE IS NOW RUNNING!!! Now, we sprung a fuel leak either in the fuel line coming in or the return line. Gotta order that part now.

BTW, we no longer need the jumper to get the fuel pump running.

alpinewhite · 10-31-2015, 03:44 PM

We still have a leak on the fuel pump on the output side where the banjo fitting is. Any tricks for getting rid of the leak? We have a new check valve and new copper washers.

alpinewhite · 10:44 PM

I found this product from another forum where an aircraft mechanic swears by this product. He claims that aircrafts can't afford to have leaks. Has anyone here used this? I plan to use this to help seal my fuel leak on the banjo fitting on my fuel pump output.

https://www.aircraftspruce.com/pages/ep/lubricants/ezturnlube.php