Fuel pressure on 944

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Andre - 29 Mar 2008 02:19 GMT

Working on an '83 944 that I replaced the head gasket on this winter. Just
started it up today. To my amassment it started after about 3 cranks. It
would not stay running at ideal, I had to hold down on the accelerator. I
check all the vacuum hoses (some were still loose) all are at the correct
place. Still same problem and now it's very hard to start. If it does
start it kills after about 1sec. I took my fuel pressure gauge out and
found that the pressure is at about 40lbs with the relay pulled and jumped.
When I install the relay I don't get any pressure when I turn the key on (is
this normal) and only about 5lbs while it's cranking and some times not even
that much. I took out the relay and tested it with 12v jumper and it's
working fine. I also have a spare DME and switched it with the same
results.

Any ideas?

Thanks,
Andre

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William Noble - 29 Mar 2008 07:34 GMT

there is a diagnostic flow chart in the porsche service manual - I believe
you have a set on CDROM, no? I would try that flow chart first and see
where it takes you. 40 PSI is the right fuel pressure.

> Working on an '83 944 that I replaced the head gasket on this winter.
> Just started it up today. To my amassment it started after about 3
[quoted text clipped - 13 lines]
> Thanks,
> Andre

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darthpup - 29 Mar 2008 14:15 GMT

Go here to check the fuel pressure for that model: www.clarks-garage.com.
I think 28 to 30 is correct.
The air flow meter may be sticking. Use some gum out on the gate
valve in the air passage.
Maybe a simple adjustment of the idle screw is needed???

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Andre - 01 Apr 2008 23:19 GMT

Thanks for the tips guys. I finally had time to check out the fuel
troubleshooting steps. I found that the fuel system is working correctly.
I have good flow, good pressure and the leak down test was also good. I
also checked for proper signals to the DME.

So I looked at the spark next. I pulled #1 spark plug and found it only
spark about every 5 sec...not good. So I looked at the coil next and found
that the resistance is good on both primary and secondary windings but when
I use the jumper trick I get very little to no spark. The only thing I can
think is that the coil is bad although the resistance measures good.

I'll let you know the outcome once I get a new coil. Just one more thing to
buy.

Andre

> Working on an '83 944 that I replaced the head gasket on this winter.
> Just started it up today. To my amassment it started after about 3
[quoted text clipped - 13 lines]
> Thanks,
> Andre

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