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Join Date: Jul 2018
Location: Canby, Oregon
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Porsche Crest No spark sometimes no fuel.

I've been trying to get my 951 started for about 4 months since the time it didn't start in June. At first it wasn't sending power to the fuel pump, so I replaced the DME relay and fuel pump fuse. After that it still didn't run the pump. I tried using a jumper for the relay and it did run the pump, but the car didn't start. I checked the plugs and it was getting fuel since they were fouled and smelled, but they didn't spark even with a test light. I checked the ignition coil and it was getting 12 volts to all three terminals. I tested the resistance, and the black terminal + the green terminal tested only 0.1 ohms above spec, at 0.7 ohms. The green terminal + the output to the distributor was more than in spec at about 5800 ohms. Could this keep it from sparking at all? It seems like such a small amount out of spec that you would think it'd at least have a weak spark. Thanks for your help.

Old 10-15-2020, 08:09 PM
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Are you getting a tach bounce? Is your battery fully charged? How old is the gas? Is the engine block grounded to the rest of the car? These are things I would check in this order. Keep us updated on your progress.
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Old 10-16-2020, 08:00 AM
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There is tach bounce, the battery has been on a tender for months, the gas is only a few weeks old, and I don't know how to check the ground. The car has no rust, so I don't think the ground would just come off by itself.
Old 10-16-2020, 04:44 PM
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Sounds like a computer issue, but you should really follow the DME test plan for your troubleshooting.
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Old 10-17-2020, 02:38 AM
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How would I go about doing that?
Old 10-17-2020, 01:44 PM
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Old 10-18-2020, 07:01 AM
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Thanks, I'll check it out.
Old 10-18-2020, 11:34 AM
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It's not a DME relay since I got a new one and tested both of them. It's not a fuel pump because it runs with a jumper on the DME relay. It's not a fuel pump fuse because I've replaced it with a known good one. I know it's not reference or speed sensors because I'm getting tach bounce. Although I'm not sure about the DME control unit, security system, or the ignition system. I think the security system is most plausible though since there is neither spark nor fuel, but I can't find the security module under the passenger side footwell. The plot thickens.
Old 10-18-2020, 11:43 AM
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Quote:
Originally Posted by Owl2059 View Post
but I can't find the security module under the passenger side footwell. The plot thickens.
Mine was missing too but was replaced by a connector that jumped the wires to bypass the alarm. Unfortunately the spade connectors in the matting connector were crap and gave a intermittent starting. I got sick of that and just used nice sealing butt connectors and haven't had a problem in 3 years.

https://www.pelicanparts.com/techarticles/Porsche_944_Turbo/36-ELEC-Troubleshooting_the_Alarm_System/36-ELEC-Troubleshooting_the_Alarm_System.htm

Mike G.


Last edited by Mike Goebel; Yesterday at 06:23 AM..
Old Yesterday, 06:20 AM
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