928 S4 Turbo

Hi,

New 1989 928 S4 owner and new to the forum. I'm Tim.

I recently purchased the former p9 Motorsports 1989 928 S4 with the rear mounted turbo (Tacoma, WA). Former owner perhaps was known by some of you on here as I believe that at one time he posted quite a bit.

I have tried to read up a bit but am new to the 928. I have a no start condition.

The car will crank and I hear relays click and hear fuel pump run. Not getting spark and not getting fuel flow at rails (loosened hose to check). Shotgun replaced CPS sensor to no avail. Have checked all 53 relays in horn position and they work.

Guessed that it could be an alarm issue so we removed alarm unit(behind glove box) and jumpered 2 positions on plug as read in a post here on Rennlist. Still no start and alarm lights on door lock pins still blink. Car cranks but somewhat slowly even with full battery, I think that I read that 928 crank slow anyways, correct?

Wiring looks to be a little of a mess with a few terminal blocks of some sort jumpering off of wires to fuse box. Will have to sort this eventually but really don't know where to start with this mess.

Thinking of pulling upper fuel pump to test but wanted to get other opinions first.

Thanks,
Tim

Mrmerlin

spray some ether into the intake,
crank and see if it fires
post a picture of the engine.

since you ID the relays ,
put your finger on the fuel pump relay,
crank the engine and see if you feel the relay click once the the engine starts cranking.
if so then attack a test light to the hot side of the fuel pump,
and see if the lamp comes on once you crank the engine

ddire333

Does radio / dash drop out when in cranking position?

928 S4 Turbo

Will check items as advised and post back as soon as I can.

Thanks again with the quick replies - I really appreciate the help!

Shark2626

Louis Ott at performance928.com can test your LH and EZK, before you chase stuff all over the car.

https://www.performance928.com/home.html

Just wondering, did you acquire the car in this condition, or have you been doing some work on the car and this occurred, or did it just happen out of the blue?

Wolfman928

Crank slowly even with full battery you mentioned ? are you sure the battery is ok ?

mine crank's fast and starts, if I have a slow crank it will barely start.

regards

928 S4 Turbo

I acquired the car in the non-starting condition. The car had been sitting for a couple of years from what the previous owner told me.

I did have the battery tested at the local O'Reilly's and it passed for what that is worth. I have also thrown in another battery in to test starting with the same no-start result.
I found an old post here on Rennlist that the previous owned made stating the non-start condition happening to him. I am trying to track down his old post as I have seem to misplaced it.

Shark2626

It would be great to get more information from you, and for you to get more information from the previous owner. What has been done by you and the previous owner to resolve the issues, and what parts have been tested or replaced. Why is the CE panel rigged; is it related to trying to resolve the no start or just some accessory like a stereo or something?

Here is a useful link. It is useful if you understand it completely because he doesn't exactly spell everything out in great detail, but he does try to point out key common issues, one or two of them may be yours.

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

GregBBRD

Slow cranking with a known good battery can be a sign of severe TBF. (TBF so bad that the crankshaft is rubbing on the webs of the block.)

Put it in the air, get the lower bell housing off, loosen the clamp bolt on the flexplate, and check the endplay of the crankshaft. (Volumes about TBF written, on this Forum, with detailed instructions on how to test it.)

928 S4 Turbo

A few more bits of information that I discovered today. Again I am new with this car so hopefully I am heading in the right direction but I am just trying to analyze and not start changing anything at this point.

1. The alarm unit has been pulled and the connector jumpered according to info found here to try to eliminate this being a cause since the lock pillars always blink when the ignition is on.

2. Crank Position Sensor was replaced.

3. When cranking I am not getting any spark at plugs.

4. Upper fuel pump not running when ignition on or when cranking. Checked voltage at Fuel Pump plug and getting +5v when key on and +5v when cranking. Checked FP fuse and swapped 53 relay with known good one tested in another position in CE panel with no change.

5. FP relay location on CE reading +12v to position 30 and 1.8V to position 85 when ignition off.

6. Ran test jumper between FP motor plug "ground" and FP relay plug location on CE and get continuity with 30, 86, 87 (battery disconnected)

7. Ran test jumper between FP motor plug "+" and FP relay plug location on CE and get the following readings: 85 open, 30 238ohms, 86 232ohms, 87 260ohms. (battery disconnected)


Getting any further information from the previous owner is probably not possible now. When I bought the car from him it seemed that he just wanted to move on and either didn't know or didn't remember what was or wasn't done with car. I will try to contact again but am not expecting any further insight.

Thanks again for walking a Noob through this!

Mrmerlin

Replace the crank position sensor with new bosch part,
don’t buy cheaper electrical parts

what is the result of the crank end play check
note don’t crank till you have completed this step

Shark2626

Your best bet would be to search your local community for a genuine "old school" Porsche specialist with first hand knowledge of 928 cars, meet with several of them, and then have the car towed and let your choice of specialists diagnose your issues and start the car. Plan on spending $1K-$1.5K just to get it running. In the long run this could save you so much time, frustration, and possibly money. To back that statement up, all you need to do is look at the previous owner of this car and how things ended for him. Its always fun to hear when someone buys one of these that won't start on the cheap, pops a few new relays in, and she fires up! But...

No one here can see or touch your car, the more information you provide (photos too) the better the input you will receive. What others have already passed on to you, > please try to do those things if you have the skills <

1. I already said this, but... Send the LH and EZK off to Louis Ott to have them tested. You can trust Louis, if they work fine he will promptly return them to you; if not, he stocks and can send you rebuilt unit(s). You'll need to disconnect the LH and EZK, obviously, so WYAI inspect the connectors for corrosion that can form in there.
2. Clean and retighten ALL of the grounds on the car (do a Rennlist search), and super clean and retighten all of the red wires in the trunk (several are attached to the battery).
3. Make sure your battery ground strap is robust, not corroded. Clean the contacts and tighten down fully. Batteries last about two years, if yours is that old plan to buy a new one, regardless of what your LAPS says.
4. Put new relays in the three key spots. Testing them in the horn spot is fine, but there have definitely been relays that work one minute and not the next.
5. Is it an auto or a manual? Check the kick down relay spot and make sure the correct part number of relay is in there for an auto (it is not a 53), or confirm that there is no relay there for a manual car.
6. Pull the CE panel and figure out why the rigged wires are on there. I would remove all of them once I determined what they each relate to, but you haven't said if you have custom accessories in the car that relate to them or not. I guess if you do then you may want to keep them, but it really is something to look at carefully. While it is out you can inspect the back for damaged or burned wires, clean the board, the fuses, and the relays, and apply DeOxit.
7. ​​​​You know now that its not the alarm, so reconnect that and put it back in place.
8. $ Replace the temp sensors with new Bosch. Yes you could test them, but for $20 bucks a piece its no big deal.
9. $$ Replace the ignition switch. It's $175+, so save for last? Up to you.

Anyway, those are a few things that you can do that are relatively inexpensive and may get some positive change(s) that can lead you to ultimate success. Good luck!

928 S4 Turbo

Hello all!

Sorry for the delayed update.......

The car is now starting! Yeah!

My 25 yr old son is already an automotive genius and himself has a 1987 944 S that he does all of the maintenance on and he has been sorting the issues on the 928.
Main issue was a broken wire on the CPS that we didn't catch when installing the new one since it it was away from the connector.

will update as we find more issues! Thanks again for everyone's input and suggestions - good times ahead!

John Speake

For future reference, you must have spark before the fuel pump is energised by the LH ECU. That is because the LH is 'woken up' by the correct signals on pin 1 from the EZK ignition ECU. Welcome to Rennlist !

slownrusty

Congrats on getting the car started. I would love to see pictures of the turbo set-up