85.5 944 New Project + No start

[Llamalord478]

About a year ago I bought a 944 hoping to make it my next daily, drove it two hours home and ran it about a week until a no start forced me to move it into the back of my dad's garage while I attended Uni. Now that I'm back for the summer I plan to crack open the project again but this time with more information. Since it was benched me and my dad have done quite a bit of work to it; replacing a ton of problem parts and bad wiring, yet our no start is persistent. I'll list what we did in as best order as i remember it. The main issue revolves around the fuel pump not sending fuel to the rail.

New battery, spark plugs, speed + reference sensor, and DME relay. We noticed it was a fuel issue so we assumed the DME and sensors would fix it but alas we had more problems.

Next we replaced the ailing fuel pump and fuel filter, and made sure everything was wired properly there and now could be forced to run manually. Also the line from tank to pump.

We then discovered multiple electric issues, and ended up replacing the ECU, engine wiring harness, distributor cap and rotor, and ignition coil. We also took apart the fuse box and tested some connections and cleaned it up. Also we replaced some vacuum lines and did some other unrelated stuff like sunroof maintenance and re-sealing the back window.

That's where we're at now, It cranks and sparks but still won't send fuel. We can bypass and force the pump to run and it will fire, but nothing happens under normal circumstances. I believe that the Tach rises when on, but no bounce. Our current suspect is wiring from the the ignition not reaching the ECU or fuse-box. Anyone have any tips or ideas before we end up tearing the dash apart? I can grab pictures tomorrow and do any tests you all will have to help narrow it down. Thanks!

[rufrob]

Is there an aftermarket alarm?
Does the pump prime when the ignition is turned on? Could need a cleaning.
Does the tachometer bounce when cranking? Could be out of adjustment.
I would check the key is making the proper contacts.
When these cars sit for a long time it take a while for all systems to wake up.
My project car too would not send fuel. After a few direct jumps at the pump it starts normally.


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[OK-944]

I tore my hair out in similar fashion after I'd completely rebuilt the engine (plus lot of other stuff) on my '87NA...chased invisible gremlins for about a month, until I removed the ecu and noticed that the alarm had never been jumpered out...a very simple procedure that only takes a few minutes. (Lots of references/info/instructions for this on the net)

You mentioned that you'd replaced the ecu, but I don't think this would alter the fact that you may still need to jumper out the alarm.

[walfreyydo]

Lacking fuel, you should run through the steps on Clarks testing the following:
-Check fuel pressure at the rail, is it reading anything? If so, is it within spec? Spec: https://www.clarks-garage.com/shop-manual/fuel-01.htm
-If no or low fuel pressure follow the steps here to troubleshoot fuel supply issues: https://www.clarks-garage.com/shop-manual/fuel-16.htm


Based on your description, we really need to verify what the fuel pressure is at the rail. Just "having pressure" isnt enough to diagnose issues with the FPR or the pump/filter/tank screen. We really need to know the exact pressure to verify startup and running pressure.

Secondly, I would recommend jumpering the DME relay while testing everything.

If you have the DME relay jumpered, and your fuel pressure is within spec, and still no start then its the injectors that arent firing. One cause could be your speed and reference sensors/harness. See the bottom of the Troubleshooting Fuel Supply section under "Other Fuel Related Issues" for other causes and ways to test.

https://www.clarks-garage.com/shop-manual/ts-01.htm
http://www.clarks-garage.com/shop-manual/eng-15.htm