No spark, no tach bounce. Crank but no start. DME issue?
 

Hey all, I’m back again. My project 944 is now back in 1 piece with a bunch of new parts. I put the new battery on and the car cranked but no start. I replaced the plugs, injectors, fuel pump, filter, soft lines in the rear, distributor cap, spark plug cables, and DME relay (with a bunch of other stuff). I took the plug out and did a spark test and saw no spark coming from the new spark plug when cranking the engine. I also smelled gas coming from the spark plug hole so I’m assuming my injectors are good. I also cracked the high pressure fuel line at the front of the car and had some gas come out so I don’t think fuel is the issue. My question is that when I crank the car, I have zero “tach bounce” so I’m assuming it’s an issue with my 2 sensors. The tops of the connectors look ok, I didn’t check the physical sensor yet. Does this sound like a DME related issue? I did order a new ignition coil and rotor because I want to
replace them anyway. The car hasn’t moved in about 15 years I would say. Let me know if starting with the DME is a good place to start when figuring this out. Thanks!

try this site:
https://clarks-garage.com/shop-manual/ts-01.htm#fire

The car has not been started in 15 years?

Does the car have a factory alarm system? (look for the "extra" keyhole on the drivers side, on the rear side of the door frame). If so...look at the DME computer box to see if its been jumpered at the correct pin locations to delete the alarm unit, otherwise the car might be impossible to start.

When I'd dropped the engine of my '87NA to rebuild it and do lots of other stuff (which became an 18 month project)...the car behaved just like yours when I'd tried to restart it - and I really tore my hair out! The alarm system was my last thought because I'd driven the car before the rebuild and had not problem. I actually removed the DME computer and opened it up, reflowing a few solder joints that did not look quite perfect. Still...no start. So just for jollies I followed the alarm jumper process (I think from Clarks?) - which was very easy and took just a few minutes and...bingo!

Not saying this is what's up with your car - but a very easy thing to check!

OK-944 Thank you for the tips! I just checked my alarm system “roughly” and tried to do a reset by locking and unlocking the doors in which I saw the alarm become engaged and disengaged it. Tried cranking and still the same thing. Still zero tach bounce too. The next thing I could try too like you said is the jumper which I will anyway because I don’t need or want the factory alarm engaged at all. Until then I’m going to still install my new ignition coil and rotor since I should have to begin with when I replaced everything else. I’ll try cleaning my speed sensors too because I’m sure they have some nasty stuff on them after 15 years

Thanks! Yea I’m going to start down this wormhole soon. Just hoping it’s not a major computer issue. The interior of the car was in great shape when got it too. No water or anything like that inside so I’m
Hoping the DME computer isn’t fried

On Clarkes there is a recommendation on how to jumper the DME relay. This allows the DME and the fuel pump to be directly powered. if it still doesn't have spark then the DME or the coil could be faulty. If it doesn't have fuel it could be the fuel pump.

However if the the car hasn't been started in 15 years you should be worried about the timing belt snapping and bending the valves. The 944 has an interference engine and if the belt snaps you will bend some valves, and need a new head or some new valves. The lifespan of the timing belt can be as little as 5 years.

IF IT WERE ME I WOULD REPLACE THE TIMING BELT BEFORE ATTEMPTING TO START IT.

I did! Water pump, timing and balance shaft belts, pulleys and a few other things have been completely replaced! I agree, I didn’t want to risk it. Now everything is back together!

sounds like there is no pulse, no tach bounce was important.

Id verify with a test bulb across the coil , crank it if the light doesn't blink, dont a
waste your money on a coil , you have no primary winding pulse.

you can verify the pulse from both sensors with a scope, someone suggeted connecting those ot the input of cheap radio that has a microphone input, If you did that you'd hear the pulse

maybe have a look at the wiring from the sensors, as the engine shakes gets hot and pukes oil fumes the wires might harden up and maybe become intermittent.

the DME relay feeds power to the DME and the fuel pump and you seem to have proven that you have fuel flow.

id look in clarks garage to se if there is a preocedure to check if the relay is latching and powering the DME. Im not the best one here ot describe how to do that. I think the newish solid state relays have LED's that may verify that. Or it is probably possible to just use a light bulb por a meter, you need ot get on the right wire.

that , I think it's a hot may be disabled by a fault in the alarm? maybe its fused, check fuses.

I'd doublecheck check battery connections and grounds and maybe try the fix on clarks garage to disable the alarm system?

you can replace sensors but if you don't get them positioned right or you get a faulty one then you may create a SECOND reason for it to not start.

I'd refrain from any "upgrades" what you want is to solve the issue not make things more complicated.

If you add parts all well and fine, but Id solve it first , upgrade later, so that
you aren't adding to the confusion.

Expecting it to start by replacing the coil when you have no pulse at the primary coil is like giving a guy a knee transplant so he can walk better while ignoring the fact that he has no heartbeat ;-)

it could be a sensor issue , cleaning wont hurt but if replacing one sensor fails to give you any joy I'd put it back and try not to create that second issue. also be perceptive about it's bracket and maybe take pics and measurements. the thin part of a vernier calliper may be handy to verify its depth now , then if you disturb that, you know where you started.

somethign easy ot miss is a bad battery ground, follow the cable and clean it where it connects. youcan verify that easily.. just place a jumper from the ground post to the engine or to the body or both and try cranking. if it starts it proves a bad ground,,

also you know the battery to starter is hot but any little red wires near that hot post? check those too. you might find a smaller red wire married at the post and perhaps left loose?