This totally confuses me (sponsor peek at this)

[Luckyman01]

Crank, no start condition. I jumped across the fuel pump relay per process found for testing fuel pump in 101 projects.

Car fires up and runs. Great news, I order a new fuel pump relay from Pelican. Upon arrival, I plugged the the relay. Crushing no joy, car does not fire.

I pulled that relay and put the jump wire in again. Car starts and runs now again.

I am frustrated beyond rational thought.

I think it is unlikely that I got a bad part. However anything is possible.

Does any run have any other leads for me to chase.

[dghii]

That means you're not getting a signal to the relay coil to turn on and provide power. When you jumper, you are bypassing the relay coil and jumpering 12v to the pump.

Need to investigate why no signal to relay coil.

[Luckyman01]

If I am not getting current to the relay, what else could it be?

David

[JFP in PA]

In order for the car to start, the DME has to see a signal from the crank position sensor telling the DME that the engine is rotating, it then turns on power to both the ignition and fuel pump. If the DME does not see that mV signal from the CPS, the fuel pump will not get power, and the car will not run.

[Luckyman01]

However, I replaced about 5K miles ago and the tach needle appears to move (ever slightly) so I dismissed that.

I am however unclear on how much movement I should see out of the tach.

Is there any support for ignition switch theory?

[blue62]

Originally Posted by Luckyman01

However, I replaced about 5K miles ago and the tach needle appears to move (ever slightly) so I dismissed that.

I am however unclear on how much movement I should see out of the tach.

Is there any support for ignition switch theory?

You could test the CPS with a volt meter at the nearest connection by back probing or unplugging the connector and probing the CPS side.
When you crank the engine you will get a signal if the CPS is good.
That way your no longer guessing if the CPS is good or not.
Or I believe you can check the CPS signal with an OBDII reader that has a Porsche program.
Like a Durametric or Foxwell

[JFP in PA]

I would be checking the CPS signal at the DME plug, which takes the entire harness into consideration.

[blue62]

Originally Posted by JFP in PA

I would be checking the CPS signal at the DME plug, which takes the entire harness into consideration.

That is also an option.
When testing something that generates a signal or a voltage like a CPS or a car battery
I try to start closest to the signal source when possible.
That way if the signal source tests good it is a wiring or connector problem.
If I start from the far end and don't get a signal I don't know if it is wiring or a connector or the signal source that is at fault until I do more testing.

[Homeoboxter]

Originally Posted by blue62

That is also an option.
When testing something that generates a signal or a voltage like a CPS or a car battery
I try to start closest to the signal source when possible.
That way if the signal source tests good it is a wiring or connector problem.
If I start from the far end and don't get a signal I don't know if it is wiring or a connector or the signal source that is at fault until I do more testing.

I think if the CPS or the related wiring was bad then the engine wouldn`t run with the pump relay bypassed. He started the thread with stating he jumped the relay and the engine ran fine.

[blue62]

Originally Posted by Homeoboxter

I think if the CPS or the related wiring was bad then the engine wouldn`t run with the pump relay bypassed. He started the thread with stating he jumped the relay and the engine ran fine.

You have a good point.
My idea of checking the CPS with a volt meter is that it is the easiest quickest way to confirm the condition of an electrical component and any wiring or connections involved as part of the diagnostic process.
No need to remove or replace the part if it tests good.
Totally eliminates becoming a parts changer and tail chasing. (where electrical parts are concerned).
Never could understand swapping electrical parts side to side (like coil packs or o2 sensors) to see if the fault moves with the electrical component.
Or replacing an electrical component because it is thought to be at fault.
When all you have to do is use a volt meter and back probe a connection or use the needles and pierce the wires.

[Luckyman01]

Full disclosure, I am not the best with a voltmeter, how I should be able to test for voltage and continuity.

However, is there general consensus that because the car runs with a jumper in place the cps is OK?

IKE84 states,
"]This may actually be due to your ignition tumbler. If your dme is dry and all other systems are working properly, but your relay is not energizing while starting, I would look at the ignition wiring and tumbler.

I noticed that when I put the jumper in place, the fuel pump fires up before I turn the key. Does this Support Ikes thoughts?

When you guys refer to the DME, is that the box in the trunk behind the carpet? When my immobilizer was rained on I sent the board from under the seat and the what I thought was the CPU to folks in Florida.

jfp states; I would be checking the CPS signal at the DME plug, which takes the entire harness into consideration. I feel clueless, is this the box behind the carpet and do I just need to become more learned of the wiring diagram in the Bentley book?

blues62, I live about 100 miles west of you so maybe one day we can meet F2F.

Anyhew fellas, any more guidance is welcomed.

[ike84]

I agree with jfp. Your dme is likely not firing up the relay. This may actually be due to your ignition tumbler. If your dme is dry and all other systems are working properly, but your relay is not energizing while starting, I would look at the ignition wiring and tumbler.

Fun fact - while the tumbler is a wiper switch design, there is also a switch at the very base of the key slot that gets depressed when the key is inserted. This is the signal to the dme that there is actually a key in the tumbler! No pushy = no bang bang.

Sent from my SM-N976V using Tapatalk

[JDMsurprise]

I had the exact same symptoms. Fuel pump relay was not triggered when turning the key to the run position. My problem was bad chassis ground for the circuit. The ground for this circuit is behind the instrument cluster. I believe my nut simply fell off and the eyelets were making intermittent contact.

Sent from my SM-G781W using Tapatalk

[blue62]

Luckyman

If I was going through the same issue...since the car runs if you jumper the relay then the problem seems to be voltage supply to the relay.
So I would study wiring diagrams of that side of the voltage supply circuit.
From that possibly I could come up with a plan for testing that circuit out via voltage drop tests.

As JDMsurprise experienced most electrical issues are bad ground issues.

[Luckyman01]

I will do some more investigation based on all the input and get back ltr

[ike84]

Hey lucky, I responded to your pm.

Let us know what you figure out.

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[Luckyman01]

Have not figured anything out except that installing a cps did nothing to help.

And input from Ike plus how loose the key is in the switch, I am starting to go toward the mechanical part of the switch. I have no idea what the implications about the imobilizer might be.

I do have a electrical part of the ignition that I may install tomorrow, wife willing.

David

[Luckyman01]

I feel like I am just throwing parts at her now without success. Yesterday was about the electrical part of the ignition switch, replaced with new, no improvement.

I guess I will look at the mechanical part today,

Really bummed,

David

[blue62]

Originally Posted by Luckyman01

I feel like I am just throwing parts at her now without success. Yesterday was about the electrical part of the ignition switch, replaced with new, no improvement.

I guess I will look at the mechanical part today,

Really bummed,

David

Some testing with a Digital multi meter would be better way to go.
You could start at the relay and test the wiring and connections back to the DME.
Or start at the DME and see if your getting voltage from the DME for the relay.
You need wiring diagrams so you know what is what.

[Luckyman01]

I do have a Bentley book and will try to do this,

Thanks guys