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-   -   DME problem? (http://forums.pelicanparts.com/showthread.php?t=955266)

944cabby 05-02-2017 03:28 AM

DME problem?
 
Hi all,
My 944 s2 cab has been laid up over the winter and now the time has come to get her on the road again for summer.
I bought a new battery, connected her up and turned her over but she refuses to fire up!
I've put fresh fuel in, all the electrics etc appear to work and she is sparking on all cylinders, but i'm pretty sure i cant smell any petrol fumes, and i cant hear the fuel pump priming, so i'm thinking fuel starvation.
I was going to start at replacing the DME, but if that was faulty would i get any spark?

dgcantrell 05-02-2017 05:04 AM

First thing to check is the DME Relay. You can jump the DME and fuel pump portions of the relay and see if it runs. If it does, the relay is defective. It is a common problem. Here is some helpful information on that relay. DME Relay Information and Testing

v2rocket_aka944 05-02-2017 07:42 AM

fuel pump does not prime.
fuel pump only activates during engine cranking.

944cabby 05-02-2017 07:59 AM

But if the dme was faulty would i still get a good spark?

944 Ecology 05-02-2017 10:42 AM

Quote:

Originally Posted by 944cabby (Post 9572652)
But if the dme was faulty would i still get a good spark?

Possible that the circuit that drives the injectors in the DME is bad, while the circuit that drives the spark is still good.

944cabby 05-02-2017 11:51 AM

Quote:

Originally Posted by dgcantrell (Post 9572423)
First thing to check is the DME Relay. You can jump the DME and fuel pump portions of the relay and see if it runs. If it does, the relay is defective. It is a common problem. Here is some helpful information on that relay. DME Relay Information and Testing

Just tried jumping the dme and its made no difference.
Engine turns over, very good spark, but isnt firing up at all.
I guess i need to check fuel is reaching the engine now.
Where should i check first? Fuel pump or fuel lines in the engine bay?

944 Ecology 05-02-2017 11:56 AM

Quote:

Originally Posted by 944cabby (Post 9572965)
Where should i check first? Fuel pump or fuel lines in the engine bay?

Check at the test port on the fuel rail (under the large black cover on the top of the engine, there is an acorn nut (17 mm IIRC) and a sealing ball bearing under the nut. When you remove the nut, a spray of fuel under pressure should come out (do it on a cold engine). If there is fuel spraying, you will need to see if the fuel injectors are getting fired by the DME... you will need a noid light for that (available at NAPA).

dgcantrell 05-03-2017 06:04 AM

If you jump the fuel pump section of the relay, you should hear it run. You should also feel fuel running through the fuel rail. If not, check the fuel pump fuse about an inch away. Also the tachometer needle should bounce slightly indicating the flywheel sensors are working. If the fuel pump does not run with the jumper installed, it is probably the problem. Start with the simple stuff first instead of throwing another DME at it. Just about every time I've had a non-start issue, it's been a DME relay, reference sensor, or the fuel pump. Never the DME itself.

944cabby 05-03-2017 07:05 AM

Fuze is ok, and the rev counter was bouncing when trying to turn it over.
I suspect the fuel pump tbh as previously when sat in the car i could hear the pump and now theres nothing.
DME relay is delivered tomorrow so i'll change that first.

Pauld_94S2 05-03-2017 11:25 AM

Did you check the fuse for the fuel pump?

944cabby 05-04-2017 02:43 AM

Quote:

Originally Posted by Pauld_94S2 (Post 9574299)
Did you check the fuse for the fuel pump?

Yeh, that seems fine.

dgcantrell 05-04-2017 03:27 AM

It's probably the pump itself. I've had the same thing happen. Especially when it's sat for a while. Especially with ethanol/s**t gas..

Toast54 05-04-2017 07:41 AM

Quote:

Originally Posted by dgcantrell (Post 9575033)
It's probably the pump itself. I've had the same thing happen. Especially when it's sat for a while. Especially with ethanol/s**t gas..

The fuel pump went out on my 924S, so I purchased one from AA (Auto Atlanta, not ******** AZ..thought I should make that distinction) and it lasted all of 15 minutes before it crapped out. Had to go through the hassle of getting another, paying for it and returning the defective for credit..on the plus side, it's been fine for the last 4 years.


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