MM951

not regular but erratic to steady flashing (almost solid light at times) sometimes when cranking there seems to be a normal flashing but as soon as it starts to catch it starts jumping around

dillon410021

maybe when you turn the key to the on position, the fuel system is purged so it is ready for when you start the car.

Legoland951

I think you have a DME problem unless there is a short on the injection wiring harness.

Oddjob

I had a similar problem that developed on my old 944S. I had tried the DME relay, ignition relay, and speed/ref sensor to no avail. Thought it must have been something with either the DME or ignition switch itself. I also had a local p-car shop look at it, and they felt it was a ground fault somewhere.

Never diagnosed/fixed the problem, and ended up selling the car (with full disclosure of the problem). New owner never told me whether he figured it out, or not.

https://rennlist.com/forums/showthre...ferrerid=15894

fwb42

Mike,
Any chance that you have used a "positive " wire and grounded it to the block or the car ? Maybe something that is isolated from the rest of the electical system and requires its own ground ?? Thus not blowing a fuse... Just thinking here.
Fred

MM951

pulled the DME , when key is on everything is normal. Have a steady 12V at the DME. Tommorow AM I will pull the maxtronic and reinstall the DME and see what it does. I don't know if it is a pointless test.. will it be possible for the injectors to fire with the DME installed but no chip image (maxtronic unplugged?)

Fred, thats a good thought. I didn't think of that but I'm pretty sure I didn't do that - and it was running fine, then without changing anything it started doing this..

mike

Bri Bro

The DME grounds one side of the injectors to get them to fire, the other side is connect to 12VDC through the DME relay. The injectors are somewhat isolated from ground by the o rings so if a injector shorted to the case, it would be hard for it to get a good ground. But, one way to check this, pull off the injector connectors one at a time and see if the problem stops.

Next, the driver transistor in the DME is going bad or the DME is firing the transistors randomly or a noisy ref sensor is randomly telling the injectors to fire.. Pull the pin that goes to the injectors out of the DME, should have two wires on it. If the problem goes away, the DME is firing the injectors. If it continues, you have a short from one of the DME injector wires to ground.


One more test, does the spark plugs also fire when the injectors fire? That would tell if the problem is before of after the DME. If they both fire, I would look at the speed and ref sensors connections.

MM951

Hey Brian, thanks for the advice.. it is much appriecated.

I pulled every injector clip individually and the problem did not stop.

I did not pull the pins out the dme harness. I just installed them and they went in effortlessly, but when removing the old ones it was hit or miss if I damaged it. I have 001 ohms resistance on every clip too.

When I unplugged the maxtronic, but left the dme connected the problem went away but of course it won't start like that. As soon as I plug it back in everything goes crazy, similar to 924s problem in the thread.

will check on the spark plugs now

Legoland951

What you are saying is EVERY injector pulses irratically when the key is on?

MM951

Yup.

and i just checked the spark plugs.. they are not firing when the injectors are firing,.

Legoland951

You have problems with either the DME or the injector harness is getting grounded somehow. Borrow a DME and go from there.

Bri Bro

I would try and install a standand IC in the DME. I am hoping you have a chip that matches your injects. If it works, it points to the maxtronic unit.

MM951

I think I'm gonna get a regular chip to match my mods from russell and see if that changes anything... I do have another DME that didn't change the problem. I'm hoping I didn't somehow fry em but we'll see. I'm sending one of my DMEs to a lister to check in his car with his chip. If that doesn't work out I'll look further in the injector harness (brand spankin new)

for once I feel like there is a light at the end of the tunnel. If a new chip fixes it.. I'll have a 95% new car

Bri Bro

One more thought, take a real close look at the maxtronic ribbon interface cable. Look at the clip on the connectors that holds the ribbon cable on the displacement pins. Sometimes this clip will separate and some of the wires of the ribbon cable will not make contact with the pins. Each of the displacement pins needs to be centered over the corresponding wire. It is easy to shift the ribbon cable and get some of the displacement pins off center. This can cause a cable that will work for a while then some of the wires will open. Also look at the ribbon cable itself, it is easy to nick a wire in the ribbon cable and cause an open.

rberry951

Hey Mike,

I've been trying to call you, but when I call the number you gave me I get a recording saying this user doesn't have a mailbox set up. Anyway, Fast924S's problem was that he had the connector to the maxtronic off by one row of pins. This is the behavior you get when the car doesn't see a chip, and that's what the maxtronic looks like to the computer. This could be your problem as well, but either way, give me a call and we'll go over everything.

Regards,
Russell