Danton

Hi,
I haven't posted in a few years. I got married, bought a house, work, etc. So I've been lost in the 951 world. And I thought after 9 years I knew this car well enough to troubleshoot whatever problem it threw at me. Anyways, 87' 951, Kokeln T3/T4, HR MAF w/ ARC2, 52lb injectors, 3" full exhaust, S2 r&p, hallman manual boost controller. The usual upgrades from years ago.....

For some reason this afternoon it wouldn't start. That's after taking two trips in it earlier in the day. It cranks and cranks but that's all. It has fuel pressure, it has spark. I swapped out a spare DME relay to rule that out. I even put back the old air flow meter to rule out it being the MAF kit. Now a few years ago I had a loose solder contact inside the DME itself. I did a resolder job and it's been fine since. And when I did have that problem I don't remember getting any spark like I am now. The flywheel reference sensors are about 2 years old and are making good contact where they connect to the engine wiring harness so I'm kinda thinking the sensors are fine. I also checked the timing belt. It's tight and intact. I would swap out the DME/KLR but I don't have a spare one lying around.

Do any of you have any suggestions? I'm stumped here!

Thanks,
Danton
87' 951
03' 325i

PorscheDoc

Is your tach moving when you crank the engine?

Danno

Welcome back!

Check your distributor cap and rotor...

jyoon

don't take this the wrong way, but you have gas in it right? ignition coil?

jc 944

Weird - must be the phase of the moon, I'm having similar starting problems on my 87. Same symptoms - ran fine then suddenly crank and no fire. I also have replaced DME relay, checked coil....

John

Peckster

Check for gas in the combustion chamber after cranking.

Danton

OK, yes the car has gas. $39.25 worth of to be exact... ouch! The tach wobbles about 1/4 inch while cranking. What does this mean? The cap and rotor are fine. Now about checking the combustion chamber for gas. Can I do this by pulling the injectors and looking in there? I'm just going by the fuel pressure gauge. I haven't actually checked for raw fuel itself... I'll do that next. Thanks for the input!

BTW, I saw another rennlister looking for headers as his have cracked. I'm in the same boat. This became obvious about 2 weeks ago. Is $700 the best deal from TurboTim/SFR for new ones?

Regards,
Danton
'87 951
'03 325i

PorscheDoc

If your tach is moving that much, then the dme is getting a signal from the reference sensor which is good. Now look for spark and fuel pressure.

streckfu's

You checked everything I could think of. Could your timing off (belt slip or something)?

If you leave for any length of time (few hours or overnight) will it start?

Mine had an issue of not starting hot because of the crank sensors. Try to borrow a set for troubleshooting.

Danton

OK.... I took out the idle screw and sprayed start up fluid in there and it started. So I guess I have a fuel problem! Should I check for a signal on an injector? If I remove a spark plug and crank it will there be visible fuel in the chamber if the injectors are working correctly? Does this sound like my DME went bad?

Thanks,
Danton

Waterguy

You can pick up a "noid" light (an LED that plugs into the fuel injector harness) for a Bosch injector at any parts place for about ten bucks. It will flash when the injector gets a signal. Before that, check for +12V at each of the injector plugs when the key is on.

Danton

Ok..... I bought a LED test light which should be about the same thing. I put both ends of the test light into the injector harness. With ignition on, the light comes on solid. Now when I crank it, the light comes on flickering but very dim. What does this tell you? I'm thinking a weak ground somewhere inside the DME...??? Is this the case?

Thanks again!
Danton

Peckster

Just pull a plug and see if it's wet with gas after you crank it. If not, your injectors aren't opening.

Danno

"Now about checking the combustion chamber for gas. Can I do this by pulling the injectors and looking in there? "

I just pull the fuel-rail and aim the injectors sideways into a rag. Crank and see if all the injectors are firing.

"I bought a LED test light which should be about the same thing. I put both ends of the test light into the injector harness. With ignition on, the light comes on solid. Now when I crank it, the light comes on flickering but very dim. What does this tell you?"

That's correct. You should've hooked up the LED with the - end in the rear pin on the connector and the + lead in the forward pin. Then as you crank, it will flicker. This way, it simulates an injector and lights up only when it gets an injector pulse. The dim LED is due to the short duty-cycle at idle & cranking. So we know you get an injector signal.

Check for spark by pulling a plug-wire off and sticking a spare plug into it. Lay it on top of the intake-manifold and crank to see if there's spark.

Could be bad fuel pump?

Danton

Well the thing about pulling the fuel rail and cranking it is the injectors I have don't have the little grooves at the top so they are only held in place by the o-ring so they'll probably come out if I do that. The signal on the LED test light while cranking is REALLY dim, so you say this is the norm? The fuel pump makes noise so I assume it's working. Should I attach a hose the to the fuel rail and run it into a bucket while cranking? Also, I have tried cranking with a plug out and I don't see any wetness inside the chamber. And I have tested the spark and it's good..... Again, thanks for the help....

Regards,
Danton