jwbeck17

I have been working to identify why my '89 928 S4 is not starting (I replaced the ignition harness, distributor rotors, caps, coils, spark plug wires, and plugs and cleaned the grounds). One thing I am noticing is that the the starter is sounding pretty labored to me and am wondering if it is not turning over well enough to start the engine. I would love your suggestions here:

Currently the outside temp. is 36 degrees F, and I have been able to get the car started with the new harness about a week ago, briefly.

First, I trickle charged the battery to full and measured the Volts at the battery with engine off:

Prior to testing, battery has been trickle charged to full.

Battery reading after trickle charging and engine off.

I then got into the car and turned the key on without starting the car to see the battery level on the dash which reads 13V. I then start the car and you can hear the starter sound slow and struggling and does not start the car.

Lastly, I check the battery level again and it is now at 12.44V.

After attempting to start.

I suspect that either there is a weak connection to the starter or it is going bad. That may not solve my no-start issue, but may be a mitigating factor.

Any thoughts or suggestions would be appreciated.

Jason

gazfish

Are you able to measure the voltage while you’re cranking as that tells you more about the battery internal resistance and health than the voltage before/after. How old is the battery?

dimi5928

Looks like battery to me.

jwbeck17

Great questions, as I thought i had changed the battery more recently, but it looks like it was changed in 2013.

I was able to hook up the multimeter directly to the battery and put my camera on it while starting to create a video attached.

gazfish

Don't think that's low enough to prevent it starting if there's no other issues, I think I had around 10v when I did a similar test some time ago. A new battery wouldn't hurt though especially if this one's been deep discharged.

Cadillac art

i say battery.

Tony

My car used to have issues starting also...replaced the starter with a known younger one and It made all the difference in the world. There was less draw on the on the battery and it turned over with much more authority. I was having issues where the injectors wouldn't fire and i believe it had to do with the current draw that the starter was taking. Seems to have solved my issue so far...

Alan

Although its a little slow - it should have no problem starting at that RPM - so there must be another issue. Keep the battery well charged and keep going...

Note - Porsche (Bosch) '53B relays will initiate reliably at 7v and hold down to ~6v well below what the ECU's need - something like 8.5v. I'd suspect something connected via the new harness.
Check injectors, that it knows its idling, that the temp sensors are connected properly, that the ISV is connected etc. If you have a spare battery (other vehicle) you could try that - but I don't think this is the cause.

Alan

Wisconsin Joe

How old is the ground strap? The one from the negative post on the battery back to the chassis.

They get old, and while they will show 0 ohms, they don't have the ability to carry all of the current the starter needs.

A 'quick & dirty' test is to take a jumper cable (just one side of a pair) and run it from the negative post to a good ground. The upper shock mount is a good place.
This bypasses the ground strap and lets all the current go from the battery to the car to run the starter.

jwbeck17

Love the suggestion and I may try it to see what happens. However the ground strap is only 5 years old since i replaced it the last time I went cleaning the grounds.

Tony

wire an LED up to the injectors. It will flash as they pulse. I'd almost guarantee they arent opening/functioning the way that sounds as it cranks. I would start at a known good or new battery. easiest and cheapest solution at this point .

Wisconsin Joe

At 5 years, I'm going to doubt it's the problem. You hadn't mentioned it in your list of 'stuff that got replaced', and it's a common failure point.

The test is so stupid simple, it's worth a shot.

Petza914

I'd also check all the starter connections themselves including the primary ground up there. Might want to take those apart, treat with Deoxit and make sure you have good, clean connections. If a battery is 5 years old and the car isn't driven at least once or twice a week and not kept on a maintainer, the batter is very suspect..

If you do end up needing to replace the starter, the hi-torque versions I have in both my 928 and 914 are sensational. When my 928 turns over and starts, it doesn't even sound like a 928 when it's cranking.

Cadillac art

If you do end up needing to replace the starter, the hi-torque versions I have in both my 928 and 914 are sensational. When my 928 turns over and starts, it doesn't even sound like a 928 when it's cranking.


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I have no doubt the hi torque starters are awesome. I know for a fact I would truly miss the sound that my 928 makes when starting. Its so unique. Silly I know but I really love that sound. To my untrained ear it reminds me of WWII fighters turning over.

jwbeck17

Well that makes two of us. I do like the 928 starter sound paired with the solid exhaust note as it is unique. I think Risky Business sold it for me!


As for the other responses, I do agree that the failing starter/battery situation is most likely not the culprit of the no-start situation. However, it certainly ain't helping. Also i later tests last night there is more of a grinding noise happening from the starter, so I have alerted Roger. My suspicion is that replacing with a functioning starter will bring the battery performance back to more expected levels.

As for checking the starter connections, I agree that is a good area to check, however I suspect it is not my issue. I had replaced the engine harness as well about two years ago which also connects to the starter, so I think i did some connections cleaning there when I did it.

Since i can jumper the fuel pump and get fuel to the rails, this leaves electrics as the main issue. I don't believe I'm getting spark (though I don't trust my noid light test as i don't think it connected correctly to the spark plug wire). The fact that I did get it to start (though poorly) with this new harness is promising, and so i have made sure the harness connections are accurate and solidly connected, as well as grounds clean. This leaves me to believe that I either have a bad relay (please be the case), a bad injector module (original), a bad EZK module, or a bad LH/EZK computer (unlikely as this was rebuilt approx. 5 years ago). Most everything is relatively new otherwise (injectors were replaced a couple years ago along with the CPS sensor, I just replaced the hall sensor, and the TB was changed this spring). I'm sure there were some other new parts put in as well.

I'm following the linked writeup here:

https://rennlist.com/how-tos/a/porsc...r-start-383833

Any additional suggestions are clearly welcomed!