tfitch03

so our buddy vagluv had the same thing happen to him. Got the car washed then it wouldnt start. turns out the guy accidentally unplugged the DME under the car seat when he was vacuuming. have to checked to see if it is plugged in?

klokwerk

The mystery deepens....

So, I've totally gone through the connections for the flywheel reference sensor and I'm sure they're good and in the correct order.

I've taken additional steps to replace the distributor caps and ignition rotors, the ignition modules, and the both coils.
I've also replaced all of the fuses in the fuse box under the bonnet as well as the ones in the engine bay (overkill !!).

I've swapped out the Solid State DME with the OEM unit that was still working and swapped them back.

I've done all of this and still the engine cranks like it wants to start, but doesn't.
The tachometer doesn't budge. So now I'm wondering if it will even start until the engine starts up. Dunno.

I have hot wired the fuel pump and it works fine. The fuse for it is fine.

Here's the latest, I've pulled the main harness from the DME under the seat and checked pins 47 and 48 for 2V ac. I get a little more than that, but less than 3V. SO I guess that it good as far as voltage to the DME goes.

What does this mean? If the reference sensor is connected properly and is getting signal from it, through the harness to the DME but the tach isn't registering any flywheel speed, does this indicate my DME has taken a dump?

klokwerk

Update

Got a call from the Tech Officer of my local PCA and was given a sanity check. Walked through the whole thing with him. He said, 'check the fuel pump.'

After the call I got under the car and tested my fuel pump.

I hear the DME Relay click, and the fuel pump click when I crank the motor but no fuel makes it to the fuel rail!
I had pulled the hose from the fuel rail in the engine bay and had a small bucket ready to catch any gas that would come out. Nothing came out.

I'm pulling the pump off the car now and will bench test it. What the heck???

Just coincidence I guess.

klokwerk

Hey there, another update on my struggles with my no start issue.

I've sorted out my reference sensor and its connector and I've moved forward in my investigation. Thanks again for the help in that thread!

Today I pulled a plug wire and a spark plug and checked for spark. None.
I checked the +/- terminals at the coil and found I'm only getting 2.6v.
Shouldn't it be 12v?

I verified that the battery Is good, I do have fuel but don't know what .

If there should be 12v at the coil when cranking and I don't have it, I'd suspect the voltage regulator. Does that sound right?

How do I go about testing it?

Thanks again!

klokwerk

Hey Renn,

Latest in my "cranks but no start" issue.....

Over the last few months I have learned a lot about the electrical and ignition system of this car and I can tell you that I've gone over this thing with as fine a toothed comb as I can.

I'm sure that I've eliminated everything in the engine bay as being a problem but I'm still in the same place where the motor cranks but I get no spark or fuel.

I have used an oscilloscope to test all of the trigger signals for the fly wheel, the hall sensor and such. Those all check out.

Don't say the DME relay. I have spent too much time and money on different, new, already working and other cars DME relays to know that it's not the DME relay.

That said, it's not the DME relay.

I've also purchased the Durametric scanner and found no codes for the engine. ABS is a different story. Different thread. I noticed that I could check the alarm but when I scan it, the tool says it cannot connect to it.

I'm getting down to grasping as straws now. The last thing I did this morning was pull out my ignition switch and inspect it. No loose wires, connections, or corrosion. It actually looks like a brand new switch.

The only thing that I haven't touched in the ignition circuit is the alarm.
Since the Durametric couldn't connect to it I guess I don't have one? I've never seen it so don't know.

I have an '89 so its supposed to be behind the main fuse box somewhere along the fender wall.

I see this small black box back there:


Is that the alarm? If it is, how the heck to I get to it? Seems pretty well tucked in there. Remember this is an 89.

Thanks! Sorry for coming off grumpy. It's been too long since I have driven my car.

PCar SBA

Make sure you have power to the DME. Else it's likely the alarm module or the DME itself. You can bypass the alarm module. All it does is interrupting T15 (switched power from ignition)

klokwerk

That box was the alarm.
It took some serious contorting and my Wife's small hands to get it out.

Once out I noticed a rattle.

Here's what came out:





I only found one other thread here that showed how to bypass it. I think this is it, but my car still wouldn't start.



My guess, I'm not doing it right. So, I'm going back to the shop manual to find out which pins exactly I should connect.

klokwerk

Well I'm at my wits end on this issue. Car still cranks but doesn't fire up.

I have done a ton of troubleshooting and parts swapping out/replacing.
I've done a lot of testing and testing again the various sensors and valves.

I've have found a few things that might not have been the problem but needed to be fixed regardless. That explains the parts replacing.

Things like the alarm unit, the reference sensor and plug. The coils and ignition control units. Sparkplug wires and plugs.

According to Adrian Streathers book I should be hauling butt down the road in my 911, but I'm not.

So after looking at oscilloscopes until my eyes turned red, I've decided to finally tow the car to a shop to have a pro look at it.

I've called the shop and talked with the specialist and he thinks they can sort it out. I'll have to spend some time going over everything that I've done and the parts that are new. I really hope they get her back on the road soon.

:-(

Porschenut_Lee

I feel your pain. Discouraging to invest so much time and money then have to tow the car to someone else. Just think of the knowledge you have gained about the car through the process though. That is priceless in my mind and you will have a car with a brand new ignition system when done. That has to be a good feeling.

Hoping you gt it back soon!

dhc905

You've had the car for 4 months without it turning? You've got crazy patience my friend!

And sorry to hear about it; these cars are so frustrating somtimes - I'm going through my own personal hell with an intermittant CEL, but that pales in comparison to your issue.

peteho

I feel your frustrations. Not sure if i have the patience you've displayed. Hope you get your car on the road soon.

eddieb4

Mine developed the same symptoms suddenly and would crank but not start. I had my mechanic trouble shoot and he performed a vacuum check and discovered leaks on the intake system. He disassembled, cleaned and replaced a few pieces that were cracked (135k mile car) and problem fixed so far. He did try replacing dme, isolating fuel pump etc first to no avail and chased down the vacuum leaks as the culprit. My car was throwing O2 sensor codes too and are no longer present.

klokwerk

Thanks for the replies guys and for all the help thus far. I've actually had this car since November last year. I was able to drive it for a couple months and had even washed it once before!

Yes, it's been a very frustrating time. But as Porschenut_Lee mentions, I have learned a ton about this car. Just not enough.

I hope it's not something stupid, or actually I hope it is. That way it won't be too expensive!

klokwerk

Spoke too soon.

The shop ended up going through all of the same tests that I did and came to the same conclusion. My DME is toast.

So, it's off to be repaired. Hopefully I'll have the car back on the road by the end of next week. Fingers crossed.

Pichu

I hope you get it sorted out man. It's really a turn off to non-hyper DIY'ers like myself if something breaks and the fix isn't obvious. (ie I hate electrical!)

When you bench tested the fuel pump, what happened? Did it ever force fuel into the rails?

How did you check for crank spark? (I have an inline tester light/thingy, it goes into spark plug hole and spark plug wire, it shows relative strength of spark as well).

Is there a way to make/force spark? (I like to separate systems so this would be great if another way to force spark could be added independently).

Good luck man! We're listening even if we can't directly help