New to me 924S - no start

[grillage]

Hi all,

I'm new to the Porsche world. I have been deep into Audis for 10 years now and there seem to be a lot of similarities.

Anyway, I purchased a non-running 924S that the previous owner overheated and likely blew the head gasket on.




When I bought the car it was with the knowledge that a twin was placed in my local u-pull junkyard, so I knew I could get a spare engine right away. I've done enough engine swaps though that I wanted to get the existing car to at least run for a couple minutes and drive up the street and back before I start tearing it totally apart and spending $. I did grab the motor from the other car as well as a bunch of other stuff to make this one look better






Interior now all cleaned up and replaced one of the seats:






With that in mind, I am working to get it up and running. The starter spins well and I believe I have fuel. I did a compression test and got 150, 130, 175, 165 so cylinder 2 could be the culprit if there is indeed a blown head gasket

What I don't have is spark. I have replaced a couple of the known failure items, Coil, speed and crank sensors (I DO have tacho bounce when I crank), distributor cap and rotor

I have tested the DME relay and ended up pulling the whole fuse-box from the other car too. So I've tried with both relays (who both test as good)

The next thing I tore into was the DME itself. When I got it loose from the car it rattled - a bit unsettling.

This is what I found when I opened it up:



The R528 Resistor had fallen out of it's home and the R518 had one prong loose.

See below: I then soldered the resistor back in and re-flowed a bunch of other spots.





This didn't solve my problems though

Anyway, I'm stuck. is there any other tests I can/should do before trying a replacement DME?

[GuyS]

I would check your timing belt first. Just a thing with me.

Then I would confirm fuel. Do so at the fuel rail cap. this way you can be 100 percent sure. Jump the DME relay to flow fuel if needed.

130 compression doesnt scare me too much. Perhaps the head gasket survived?

[Dmitry at Pelican Parts]

Hello and welcome to the forum! To help you with getting this car running, I'm attaching a link to our site's DIY tech articles on the 924 platform. Please let us know if you have any questions or if we can assist in future part needs.

Porsche 924/944/968 (1975-1995) Technical Articles

[grillage]

Originally Posted by GuyS

I would check your timing belt first. Just a thing with me.

Then I would confirm fuel. Do so at the fuel rail cap. this way you can be 100 percent sure. Jump the DME relay to flow fuel if needed.

130 compression doesnt scare me too much. Perhaps the head gasket survived?

Yeah, the compression doesn't seem crazy low to me.
I could definitely smell fuel before so I moved on to spark. I am picking up another DME later this week so I hope to have an update after that. thanks!

The timing belt - I wouldn't have compression if it were broken or off by a few teeth. Plus, I'd still have spark - it just wouldn't be synced. I recently had my audi 90 5 Cyl swap eat a TB Cover bolt and skip a tooth. I had spark but it wouldn't run

thanks!

[grillage]

Originally Posted by Dmitry at Pelican Parts

Hello and welcome to the forum! To help you with getting this car running, I'm attaching a link to our site's DIY tech articles on the 924 platform. Please let us know if you have any questions or if we can assist in future part needs.

Porsche 924/944/968 (1975-1995) Technical Articles

Thanks for the link!

[GuyS]

Originally Posted by grillage

Yeah, the compression doesn't seem crazy low to me.
I could definitely smell fuel before so I moved on to spark. I am picking up another DME later this week so I hope to have an update after that. thanks!

The timing belt - I wouldn't have compression if it were broken or off by a few teeth. Plus, I'd still have spark - it just wouldn't be synced. I recently had my audi 90 5 Cyl swap eat a TB Cover bolt and skip a tooth. I had spark but it wouldn't run

thanks!

I am sorry. I wasnt more clear. I did not mean the timing belt was related to your problem, just reinforcing the notion of establishing its condition before jumping in on an unknown car /history.

[grillage]

Originally Posted by GuyS

I am sorry. I wasnt more clear. I did not mean the timing belt was related to your problem, just reinforcing the notion of establishing its condition before jumping in on an unknown car /history.

Oh yeah, I always change timing belts on any car I buy. This one is likely going to get the other engine after a rebuild of it. Before I pull the motor though I wanted to make sure everything else is in good working order. It sucks to put a new motor in and have to chase down unrelated problems (like a bad ECU/DME)

[Toast54]

I had an issue a few years ago where the car would start, run for 3-5 minutes just fine, and then die.
I pulled the DME box and found no obvious signs of problem. I ended up buying a known good DME from a forum member for 75.00, installed it and have had no starting issues since

[grillage]

New DME from plyhammerparts - he's about 2 hours north of me so I drove up yesterday and picked up the DME and a good driver's side door.

Sparks and now runs!

I seem to be missing in Cylinder 1 so I'm working to figure out why.

[curtisr]

Originally Posted by grillage

New DME from plyhammerparts - he's about 2 hours north of me so I drove up yesterday and picked up the DME and a good driver's side door.

Sparks and now runs!

I seem to be missing in Cylinder 1 so I'm working to figure out why.

Glad to hear! It sounds like this car has found a deserving home. +1

[grillage]

Thanks!

I am thinking I have a fuel delivery problem. Had some family obligations this weekend so I haven’t had the chance to measure flow and change out the fuel filter. Who knows what condition the gas in the car is in too