Tom M'Guinn

If the DME relay is bad, the tach will not bounce when you crank the motor, at least on my car. If you have no tach bounce, check if the boost gauge comes up to 1 when you turn on the ignition. If it does, then the DME is getting power at least and the lack of tach bounce is more likely the speed/ref sensor.

Tom M'Guinn

The factory harness has little stickers on the harness that say DG for the speed sensor (i.e., the rear sensor), and BG for the reference sensor. If the tags are missing, you can use a multimeter to determine which connector is which. The front reference sensor is connected to pins 25 and 26 and ground in the DME connector in the footwell -- just pull the connector off the DME and put one side of the meter on pin 25 and then try each of the pins in the two connectors. Whichever connector has one wire connected to DME Pin 25 is the reference sensor connector (i.e., the front sensor). If you want to double check, the speed sensor connector should have wires connected to pin 8 and 27 in the DME connector. It's easier to troubleshoot if you at least know which connector is which...

Tom M'Guinn

The flat 8 pin connector in back in the first picture drives the boost gauge and tach. Without it, you won't get anything on that gauge -- assuming you are using a turbo cluster?? Have you confirmed the oil pressure sensor is wired up correctly?

1987Porsche944WithRealLongName

I am using an n/a cluster

I haven't confirmed anything with the oil pressure sender because if the leads were wrong it'd go to 5 bar, right? At least that's what I read somewhere in search.. The needle does move a bit when I turn the motor.

I hooked up some jumpers for the dme relay and turned over, no rpm movement. However I doubt rpm is based on the same pegs as the fuel pump is so I'm probably jumping the wrong stuff for rpm anyway, and clarks doesn't really show anything related to rpm on the relay schematic http://www.clarks-garage.com/pdf-manual/fuel-05.pdf

Chris White

The tach signal comes from the DME and if the DME is not powered through the DME relay you will get no tach signal and no engine start.

A lot of older 944s won’t wake oil pressure until they start – cranking does not spin the oil pump fast enough to prime it after it has been sitting for a while.

5 seconds of run time at idle speeds will not hurt an engine (unless its new and was not coated with a good assembly lube). If that really scares you then you can pull the plugs and run the starter motor for 10 -15 seconds. The engine will spin a lot faster without compression.

All gauges except the tach will function without the DME.

1987Porsche944WithRealLongName

Had 3 bar cranking

Cylinders filled with fuel, heard a loud bam bam sound

Motor won't turn by hand, fuel pretty much filled up to the sparkplug holes.
Thanks anyway guys, looks like I'm done.

eclou

crap that sucks. The floorboard connectors are for powered seats

1987Porsche944WithRealLongName

Alright, well it turns out the crank can be turned by hand

And I read somewhere that these starters may have hydrolock protection? Considering the car never actually ran.. could I have been spared a bent rod/cracked cylinder?

I'm really lost here, what should my next step be? I was using 72# injectors I bought off a rennlister and a regular bosch 3.0fpr

Bri Bro

Cranking an engine should never fill the cylinder with fuel. The exhaust stroke will push out the air/fuel in the cylinder. So, you observed that the entire cylinder filled up with fuel? If you did, you have other issues like a leaking injector or a DME that is always signaling the injectors to open (shorted injector driver transistor inside the DME). With the plugs pulled, that would be easy to hear/see. If it is doing this, be careful that a spark doesn't set the engine on fire. I would remove power the lead from the coil.

Why didn't you pull the DME relay and the plugs before you attempted to get oil pressure? The only hydro-lock protection from the starter that I am aware of is the amount of torque that the starter can output to the flywheel. I would guess no damage but a compression check would confirm that. If you are not trusting your oil pressure connections, loosen the oil filter when you crank. It will make a bit of a mess but with a rag below the filter, it is not that hard to clean up.

1987Porsche944WithRealLongName

I did pull the dme relay and cranked for oil pressure. I had a good 3 bar or so before putting them back in.

I didn't crank long before it filled, and both the 3 and 4 cylinders had what I figured was fuel but could have been water/fuel. Will the injectors just keep spraying if the dme is messed up? How can I tell

Think my cometic headgasket from lindsey could have been botched? I haven't noticed any coolant loss but still.

Bri Bro

Good, always take the advice of Chris...he knows these cars. More then likely you have water rather then fuel. If the DME injector circuit was shorted to ground all the injector would fire as soon as you turned on the ignition. A quick way to check is to pull the connectors on the injectors and see if you still get fluid out of the plugs. Leave the spark plugs out so you don't have a hydro-lock issue. You could take a sample out of the cylinder and smell it. If in doubt, take it outside and try and put it in water. Fuel will float on the surface of water since it is less dense. Also, if you are using colored antifreeze, it will be easy to spot. If it is water/antifreeze, you need to drain your oil and flush that stuff out of your oil system. Antifreeze is bad for bearings.

1987Porsche944WithRealLongName

Pulled the plugs with injectors in, it was like geysers firing out of the holes. This may have been from a slow leak..

Pulled the wires off the injectors, it was less so but there was still squirting a LOT of liquid, it smells strongly of fuel

I'm going to let the pressure bleed off and try pulling the injectors completely out and see if they still do it, oil is showing no sign of water leakage (however the car has only pumped up to 3 bar on one occasion so there may not be adequate flow.

Bri Bro

Sure sounds like the head gasket. Not surprising the fluid smells of gas since the injectors were firing. The fact that it continued to blow out fluid with the injector plug pulled make me think it is water getting into the cylinders. Remember to pull the fuse to the fuel pump or pull the DME relay before you crank it with the injectors pulled.

I had to come in from the garage, temps are close to 100 degress so I am hoping you have some cooler working conditions.

Tom M'Guinn

If you can get a cooling system pressure tester (available at sears for under $100, and maybe rentable at your local auto parts shop), I'd pump up the cooling system to 15-20psi, and see if the cylinders fill with coolant. If so, the HG didn't take... Frankly, from your description, I'm not sure what else it could even be...

I put an split system A/C unit in my garage a few years back, and I highly recommend it.

Bri Bro

Great idea Tom, the tester will show the problem if it is the head gasket. I would also check the torque on the head bolts.
Wasn't there a problem in the Lindsey HG some time ago? I remember a post about a problem...might want to check it out.

The A/C unit does sound like the way to go. I was soaked from head to toe by the time I can in.