924Board.org

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

Well it died and now won't start, but that's not the whole story so let me give you some background and maybe someone will have some insight.

Son buys used 1987 924s. It seems to run ok but makes a lot of racket kind of a clatter sound that I can hear all the way inside the house. I think something is wrong but know nothing about Porsches so I dismiss it as "normal".

About a month later son says it is overheating so I go take a look and pop the coolant cover and notice green sludge in the coolant reservoir and water vapor in the exhaust. I ask him (knowing the answer already) if he has been racing around like a maniac, which of course he denys

Flushing of the cooling system does not seem to help, it still overheats.

I tell him best case scenario is that he has a blown head gasket and worst case scenario is a cracked head or block. We decide to make a project of it and tear it down and remove the head. The head comes back from the machine shop with the diagnosis of a blown gasket and everything else looks pretty good.

In putting it all back together we found that the lower balance shaft had been 180 degrees out of whack which would seem to account for the loud clatter sound we had heard previously. That fixed it all went back together pretty easily.

On first turn over it started right up and clatter was gone. It seemed to run real nice even better than before as we found the timing belt off by one tooth.

We were in the process of flushing the cooling system when it just up and died and would not start. We fooled around for a few hours then it started up after about 3 hours without any clear reason why and I chalked it up to getting something wet in the flush process.

Next day: Drained the water and changed the oil. No water in the oil. Filled with coolant and all seemed good when we shut the hood and it died and would not start. Suspected fuel problem. Took of the air filter and squited starter fluid into air intake and engine would fire breifly so thought the problem was fuel related. Tested fuel output from fuel pump and found that it was surpasing the amount of fuel needed as per specs. Ruled out fuel pump.

Tested resistence on fuel injectors and passed within specs. Tested voltage on injectors and passed. Tested fuel pressure by jumping terminals 30 & 87b on DME relay with engine stopped. Got 29 psi with the relay jumped which is the correct pressure for when the engine is running not when relay is jumped. Supposedly it should be 36 psi when the relay is jumpered so I kind of suspect the fuel pressure regulator.

Fooled with the vacuum fittings on the fuel pressure regulator and it started up and ran for a little while. We figured we had a vacuum leak and had fixed it with fooling with the vacuume hoses connected to the fuel regulator. Turned it off and worked on the headlight bar as the final issue (we assumed) and it would not start. Checked vacuum hoses, vacuum routing correctly, rapped on the fuel regulator a bit with a wrench and so far nothing.

That's where it sits. It just won't start at this point and am at wits ends. Any ideas or suggestions would be appreciated.
_________________
Just a regular dude trying to help son get his 924s running

Khal · Posted: Fri Dec 30, 2011 7:05 pm Post subject: Re: 924s Dies then won't start

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

If you have checked your DME relay, check you crank sensor and speed sensor output at the dme plug.

Description of plug connector can be found here.
http://www.the944.com/connector.htm

Testing

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

Get a low voltage LED and use it as a test light between the mentioned terminals. It will blink on the refrence sensor and glow on the speed sensor terminals as the motor is cranked. Very simple to do but the sensor voltage output is very low and will not light up anything that draws alot of juice. You may have to try a couple of leds before you find one that is bright enough to see. The fresnel inside the LED magnifys the brightness of the blink.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

Thanks for the help so far, however I'm a little confused now.

I got me an LED from radio shack with these specs:
FW current: 20mA
FW supply: 2.4V (max)

I think that should be sufficiently low voltage to do the test. However now I'm a little confused as to where I should be testing. I looked at the reference link located at http://www.the944.com/connector.htm. That looks like a connector (35 pin) attached to a cable. Where is that?
Everything I have found regarding DME shows some kind of a relay like mentioned in this link: http://www.clarks-garage.com/shop-manual/fuel-05.htm
So I guess my confusion is this. Is the DME connector different than the DME Relay and if so, where is the DME connector that I should be testing?

Thanks again for all the help!
_________________
Just a regular dude trying to help son get his 924s running

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

The DME is your computer. It is located under the steering column on the 924S. Unplug the long connector from the back of it and bridge the mentioned terminals with the LED.

The DME relay is just that, a relay that is located in the fuse block.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

OK, so I get a blink when jumping pins 25 & 26 but also get a blink when jumping 8 & 27 not a solid light. Any idea what that is supposed to mean?

Thanks!
_________________
Just a regular dude trying to help son get his 924s running

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

It means your flywheel sensors are most likely good. I haven't done this test in maybe 5 months or so, so im going from memory here. I was thinking the speed sensor puts out a flutter or a faster pulse than the refrence sensor, but if it is putting out enough to light up an LED chances are its good. In my experience when a sensor goes bad it dosent light up sh@#*.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

Went out and pulled the brain plug on one of the cars and checked it myself. The speed sensor pulses about twice as fast as the refrence sensor. With a good hot battery and a warm day it would be a flutter, not a solid glow. Didn't have much time for thinking about porsches at work today.

Read over your opening post again and agree that the FPR could be at fault, but it seems to me thay they usually fail either open or closed. Open and you develop little to no pressure at the rail. Fail closed and the fuel pressre on the injectors gets so high that the injector drivers in the dme shut down sensing the increased current draw. Have you tried jumping the dme relay and starting the engine? I haven't heard you say that you have ruled out the dme relay in this manner, you just jumped it to check fuel pressre on a non running engine.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

I have not tried jumping the DME Relay yet.I wanted to rule this out first. I found a page on Clark's Garage (which has been our manual for doing this project) about the DME Relay at http://www.clarks-garage.com/shop-manual/fuel-05.htm. We'll try that in the morning. I'll let you know how it goes.
Thanks for all the help!
_________________
Just a regular dude trying to help son get his 924s running

joecitizennn · Joined: 12 Sep 2005 Posts: 2096 Location: no mans land

you might try this quick trick.

In the upper fuse rail (the one that faces the floor) find the 2nd from far left fuse. This is the fuel pump fuse. take a small screwdriver or bit of wire and bridge this fuse with the one left of it which will be hot. You should hear the fuel pump kick on. Now with the fuel pump running hit the starter and see what happens.
_________________
87 924s
88 924SE gone
447 hp cgt clone
87 924S gone
84 944 sold
83 944 sold
89 turbo S LSD, ABS etc
86 951 white rocket
85 944 sport everything.
84 944 sold.
87 944 sold

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

One addition to the FPR/Damper diagnostics. . .pull the vaccuum lines off each, and sniff. If they smell of fuel, the diaphragms have failed and the units are bad. If you replace, buy new. . .it is false economy to buy used of this type of part, IMO.

Having said all that, I have doubts that a bad FPR would cause a no start situation. . .more likely DME (relay or unit itself) or flakey ignition switch.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

squoggle · Joined: 30 Dec 2011 Posts: 9 Location: Utah

So here's what I found:
Using Clark's Garage manual for testing the DME Relay: http://www.clarks-garage.com/shop-manual/fuel-05.htm

I tested resistance between pins 30 & 87b
and
pins 30 & 87
and got a 1. on my multimeter

Then connecting 12 V accross pins 85b & 87 then testing resistance accross pins 30 & 87b I got a reading of .7 - According to Clark's Garage it should be between 0.1 and 0.3 ohms. However I'm not 100% sure the multimeter is set to the correct setting. I'm kind of just guessing here as I'm out of my league on electronics.

The next step from Clark's Garage was to connect 12 V accross terminals 85 & 86 of the relay with negative going to 85 and positive to 86 and take a resistance reading accross pins 30 & 87. My reading was 1.0. According to the tutorial it should be between 0.1 and 0.3.

I'm wondering if I have the multimeter set correctly. Here's a photo of the setting on my multimeter to help in case I'm making a noob mistake:
http://squoggle.com/files/Multimeter.jpg

So in continuing along this line of reasoning we decided to make the "emergency jumper" mentioned in the Clark's Garage tutorial. Here's the jumper we made:
http://squoggle.com/files/Jumper.jpg

We connected that on pins 30, 87 & 87b under the dash. When we connected pin 30 (the last pin like the tutorial says) the fuel pump kicked on for about 5 seconds. I'm assuimg that means the fuel pump kicked on long enough to fill the lines and rail with enough pressure then kicked off once it had the correct pressure in the lines.

The car fired very breifly for about 1 second then back to not starting.

We pulled the vacuum off of both the FPR and Damper and sniffed the lines as Rasta Monsta suggested. They smelled faintly of gas, but then pretty much everything smells of gas since we spilled gas everywhere when doing the pressure test. I'm still not sure which is the FPR and which is the Damper as they look a lot alike and all the manuals we've seen show one on the left and one on the right side of the rail and not like we have with one on the front and one on the back as in this photo:
http://squoggle.com/files/FuelRail.jpg

So I guess where we stand now is we're not sure if it is the DME Relay, the FPR, the Damper or what? I go back to work on the 3rd and need my car back from Junior which he has been using in the interim

I guess it goes without saying he needs his car running to get to and from work as well. I'm starting to get the idea that this is a project car and not a transportation car!

Anyway, thanks for all the advice so far. You've all been life savers so far especially Joe Citizen! Thanks and Thanks in advance for future help!

Edit: Oh, I forgot to try the trick Joe Citizen mentioned about jumping the fuses. I'll try that next and see where we get.
_________________
Just a regular dude trying to help son get his 924s running