WICruiser

I realize that you replced the critical relays but to isolate them use a jumper rather than relying on an alternate part. In the process inspect the terminals that the relays push into - there have been cases where the terminals get pushed out the back of the panel and do not make a reliable connection.

Rod Underwood

I did check to make sure they weren't pushed out, but they all looked good to me. Maybe it's worth a second look.

Thanks
Rod

Rod Underwood

That's certainly worth a try. I'll do that tomorrow night.

Thanks
Rod

John Speake

If you have spark but no fuel pump relay energisation and injectors not firing then the rpm signal may not be getting to pin 1 LH. The tach is connected to the same pin, so shouild flicker when you crank the engine.

The kickdown relay is also fed from the same point, so remove that relay as see if that is the problem.

Landseer

Rod,
The crankshaft position sensor has failed for me on the 86 and there is a strong suspicion it failed on the 85, plus on my jeep wrangler. It provides the signal that is the basis for when the spark should happen, and is no-doubt part of that EZ, LH, Fuel pump logic train.

That's one sensor that I would suggest you consider replacing, as also mentioned above by Borland. A little reach to get to it, but not too bad.

Alan

Well obviously it wasn't the pump (keep the old one its OK), I assume you actually did get fuel priming pulses before & now when the ignition was first turned on (these are hard to discern without a helper).

So all along I think its been the rpm signal. After a short initial priming burst (when ignition is first tuned on) - the LH is designed not to turn the fuel pumps on again until it detects the engine rotating... it will stop the fuel pumps as soon as it detects the engine stops rotating - this is a safety feature. Meanwhile the LH & EZK also won't do anything unless they think the engine is rotating properly - so there will be no spark or injection pulses either...

Alan

hans14914

Rod,

I had the same problem a couple years ago (stranded me a couple times on the long drive back from Paul's). In the end, I went through and replaced all the parts that the CPS goes through - including the kickdown relay. That solved the problem. There is a domestic CPS that works well, same part with a longer lead. Its available at most local auto part stores, but DR carries it now as well as a low cost alternative. Run down the street and pick one up, part number should be posted somewhere here on the forums, if not, I can dig through my files and find the number.

Rod Underwood

I have replaced the crank sensor, so I don't think that's the problem, now have an extra fuel pump AND an extra crank sensor, but that's not an entirely bad thing.

This is the 5 speed, so the kick down shouldn't be an issue, unless you are talking about something I'm not aware of. An easy thing to do.

I'll check the tach and see if it moves when I try to start it and clean the wires on the battery as suggested above. I know it can be solved, just the time and patience to do it.


Rod

fraggle

You can isolate the cps signal from the rest of the harness by pulling wire W21 (or w23??? Argh can't rememeber). Take a look in the wsm wiring diagrams.

Currently my car only runs this way due to a short in the dash somewhere. The tach doesn't work, and my short is before the pod somewhere, I think.

There can also be a short between the cps and the computers, so the signal doesn't reach them.

An o-scope is essential for troubleshooting this one.

Alan

Regardless - I think it still is the issue.. it can be a connection somewhere so replacing it may not make any difference - check the connectivity all the way to the ECUs

Alan

fraggle

If your connectivity to the sensor is good, you may have. An issue like mine, where a downstream short is killing the signal.

I'll check my CEL tonight.

If you don't have the official porsche lh/ezk troubleshooting guide, search around on the site, someone posted some scans or at least the text within the last couple months.

Rod Underwood

Just checked it and the tach does NOT move when I try to start it. This is a 5 speed, so no kickdown relay, unless I'm misunderstanding what you mean.

Rod

Rod Underwood

Okay, I'll see if I can track it down.

Thanks
Rod

Rod Underwood

I am getting spark when I try to start it. Pulled the connector, put in a screwdriver and it sparked as the engine was turning over.

Rod

Rod Underwood

Cleaned the terminals at the battery .... nope, no difference.

Thanks
Rod