DME Troubleshooting / Repair Advice?

[Quasimoto]

Have read several DME relay threads that have been very helpful, but still needing some advice with an intermittent no start issue.

1. Once the car died while rolling, and once it wouldn't start after sitting a couple of hours.

2. Engine cranks but no fuel.

3. Battery condition is good. Alarm was bypassed ages ago using info here.

4. Can't hear the fuel pump run.

5. I have solid state relay.

6. Tried putting a known good mechanical relay in, same result.

7. Installed a 87/87b/30 jumper in the relay socket, and car starts and runs fine.

Read a couple of threads that hint at possibly bad solder joints in the
DME may be a cause. Is this plausible, and if so how best to have it repaired?

Thanks

[salayc]

Test the reference sensors. Bentley has the resistance values.

[991gts6s]

Yup DME relay ... need a spare in the glove box..
NOS old one work for very long time.. repops are crap and some dont work brand new..

[Quasimoto]

Originally Posted by salayc

Test the reference sensors. Bentley has the resistance values.

Have plans to test them this weekend, but if one was bad, how would jumpering the DME relay let the car run? (not being a wisea$$, just trying to learn)

Originally Posted by 991gts6s

Yup DME relay ... need a spare in the glove box..
NOS old one work for very long time.. repops are crap and some dont work brand new..

It's not the DME relay, car wouldn't start with 2 different functional relays.


On a related note, I wish now I has spent the extra few bucks for the "priming" version of the Focus 9 Solid State relay. I bought the basic version, and now think it would be nice to be able to hear the pump.

[uwanna]

As said previously, check reference sensors. The reference sensors (when the engine turns over) signal the DME box to energize the fuel pump relay in the DME relay unit.

[salayc]

Originally Posted by Quasimoto

Have plans to test them this weekend, but if one was bad, how would jumpering the DME relay let the car run? (not being a wisea$$, just trying to learn)

You don't jump them, just test pins 1-2 for resistance. I don't know of a way to jump the sensors, but you can jump the DME relay which will probably get the car to run.

Also, the DME relay gets switched power you can check it by removing the relay and testing the connector. The DME gets switched power (I beleive it's pin 1) If you have power to both of those, either there's a problem with the DME, or the reference sensors.

Someone else will probably chime in with more.

[Quasimoto]

Originally Posted by uwanna

As said previously, check reference sensors. The reference sensors (when the engine turns over) signal the DME box to energize the fuel pump relay in the DME relay unit.

Thanks!

[GH85Carrera]

It might be the fuel pump itself. How old is it?

The reference sensors are often the issue, but not always. If you replace the reference sensors it is often a good "while you are in there" thing to do to replace the head temp sensor as well.

[Quasimoto]

Fuel pump runs fine with the DME relay jumpered out, but doesn't come on with a known good DME relay.

[NY65912]

I sent mine to fellow Pelican Ingo Schmitz ischmitz

He went thru the DME using a microscope to check for solder cracks and resoldered a few suspicious connections. Great guy as well.

[salayc]

Originally Posted by Quasimoto

Have plans to test them this weekend, but if one was bad, how would jumpering the DME relay let the car run? (not being a wisea$$, just trying to learn)

Misunderstood your question. The DME relay get's power from the DME which then switches on the fuel pump. Jumpering it bypasses the DME as a power source.

[Quasimoto]

Thanks again!

[Quicksilver]

Seeing that you know that the DME relay isn't being triggered to "on" you only have a few choices of where to look.
- You could have multiple failed relays. (Doesn't seem likely.)
- There could be a issue with the wiring from the DME that energizes the DME relay.
- There could be an issue with the DME itself.

The first thing I would check is if there is continuity in the wire that energizes the DME relay, plus if there is a good ground for that trigger circuit.
Second is to check if the DME is generating the required current to energize the relay.
If you still haven't found the problem I'd check to see if there is a voltage drop over that circuit.

_______________________
I have to congratulate you on taking the steps with trying the 3-way jumper to narrow down where the problem lies. Too often people throw money at a whole bunch of parts and would still not have any idea where the problem is.

Good luck.

[uwanna]

The order of things when starting 3.2 DME motor:
Turn the key to start position, should hear the DME relay click. That click is the relay that provides power to the DME box and also provides 12v to injectors, coils, ICV etc.
Hint, you could check for 12v at the ICV (idle control valve)

Note that the DME relay contains two relays in the unit. The primary does as I just
stated. The secondary relay is the fuel pump relay. While cranking the motor,
the flywheel sensor tells the DME box to send 12v back to the fuel pump relay located in the DME relay unit and turns on the fuel pump.
Makes sense that you don't want the fuel pump running if the DME isn't active.
SAFETY ISSUE.

[911obgyn]

Speed and reference sensors can and do fail intermittently. Sometimes they work and then don’t. Then do.

[Quasimoto]

I believe that for sure. Now that it’s home, I poked a relay back in it, and of course it fires... :/

Still going to check the sensors when I get a minute.

Not looking forward to trying to trace down an intermittent ghost in the machine, but that’s where I seem to be at.

[mysocal911]

Remember, the alarm relay controls an input pin to the DME relay. Check the wiring diagram!

[Quasimoto]

See #3 in first post...

[mysocal911]

Originally Posted by Quasimoto

Have read several DME relay threads that have been very helpful, but still needing some advice with an intermittent no start issue.

1. Once the car died while rolling, and once it wouldn't start after sitting a couple of hours.

2. Engine cranks but no fuel.

3. Battery condition is good. Alarm was bypassed ages ago using info here.

4. Can't hear the fuel pump run.

5. I have solid state relay.

6. Tried putting a known good mechanical relay in, same result.

7. Installed a 87/87b/30 jumper in the relay socket, and car starts and runs fine.

Read a couple of threads that hint at possibly bad solder joints in the
DME may be a cause. Is this plausible, and if so how best to have it repaired?

Thanks

Then just ground pin 85b of the DME relay, i.e. don't use the relay jumper.
If you still have the problem, it's not the DME ECM, i.e. you have a wring problem or bad DME relays.

[mysocal911]

Originally Posted by uwanna

The order of things when starting 3.2 DME motor:
Turn the key to start position, should hear the DME relay click. That click is the relay that provides power to the DME box and also provides 12v to injectors, coils, ICV etc.
Hint, you could check for 12v at the ICV (idle control valve)

Note that the DME relay contains two relays in the unit. The primary does as I just
stated. The secondary relay is the fuel pump relay. While cranking the motor,
the flywheel sensor tells the DME box to send 12v back to the fuel pump relay located in the DME relay unit and turns on the fuel pump.
Makes sense that you don't want the fuel pump running if the DME isn't active.
SAFETY ISSUE.

Ground.