Hi all, I am new here as a member but have been trawling through the posts which has helped me narrow down the issue. I have a 2004 crossfire standard and it cranks fine but no fuel pump action. I have checked all the fuses i could find and no fix. I have seen many threads about the relay control module, so i took it out and did find a few real bad dry solder joints, though my issue is not the no crank but its no fuel pump. To further diagnose i bridged a wire from the +v direct to the pin for the fuel relay contacts 2nd and third pin in socket and fuel pump worked and car starts and drives perfect, remove wire and no more fuel pump. I next opened up the case so that i could see the actual relays and upon turning the key to on the fuel pump relay did not energize at all so obviously not sending power to the pump. After double checking all solder joints and measuring relay coil resistances i can not find anything wrong with the relay module. After studying the manual it looks like the relay coil is energized directly from the Powertrain control module. Now this is where i get stuck, i am struggling to find useful diagnostic info for the powertrain module not energizing fuel pump relay. When i bridge a wire for relay contacts the car starts and drives perfectly with no warning or check engine lights on dash. I do not have a scan tool to be able to plug in to see. I know you guys hate newbies posting ***** nilly, but i have studied and explored i promise lol. Thanks in advance for any help.

 

I don't know that you will ever find schematics etc on the PTCM.
I would hazard a guess however that the relay is controlled by a mosfet in the PTCM.
Maybe you could shotgun all the mosfets ?
Also, the contacts/coil for the engine control relay or fuel relay could have a problem.

 

Hi, thank you for a quick response. Ok so my next question, is there any harm in wiring up the fuel pump feed pin to an key on positive feed ? Obviously when ever the key is on the fuel pump will be running constant rather than the 2 sec burst, but is this bad, at least i can have a semi permanent fix !!

 

Why not just have DJ Tighe rebuild it for $50.00 or buy a new one.

 

HI, I wish it was that simple, I am in the UK also though I think the issue stems from the powertrain control module and not the relay itself though still not 100% on this yet as still investigating.

 

I would not feel comfortable in supplying an answer to that due to the inherent risks involved.

 

I agree with ala_xfire, especially if the fuel pump cycles per demand. Running it constantly is not a very good idea IMHO. Have you tested the input to the RCM fuel relay from the PTCM at the connector of the RCM fuel relay coil? It would involve a test lamp or voltmeter observable to the operator after the car sits a while in the off position. Of course you would have to have the open RCM sitting on top of the engine cover/box with the voltmeter/test lamp hooked up during the first seconds of turning key to 'on' position. This test would indicate the correct total path through all the connectors involved if it lights/registers. If not, then you have an answer to part of the problem. Good luck!


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electric fuel pumps run continuously, that is why the filter / regulator shunts the flow, my zeiteck monitors my pressure at about 60 #constantly and more as my boost controller ramps it up to keep fuel flow constant with the boost. I have thought of a fuel pump assist switch which would run the pump before starting to get the rail pressure up when starting . This would reduce the cranking time when the car has been sitting and the pressure bleeds off. I would monitor the relay control signal to see if you ever see it, its unlikely that the coil driver has failed, this should be metered or scoped to confirm the status of the driver circuit. keep us informed please. Woody

 

Well good news guys, after reading the reply from GraphiteGhost and his query whether I took readings from the input for coils from the PTCM it made me realise that i had not because I had measured resistance on the coil indicating it was not an open circuit so in my mind was fault free. However today I took readings and discovered that the PTCM was sending 12v to energise the fuel pump relay. So after some head scratching I took the Relay module apart again and confirmed with multi meter continuity from socket pins to coil solder pads and could still measure resistance across the coil. This was illogical it should have been working, so I fed 12v direct to the coil and it would not energize !! I dont know why the relay would not work, its contacts were nice and free and the coil measured not an open circuit. Well anyway this pleased me as I knew I could simply bypass relay with a common part from local auto store.

So for the grand total of £7.00 for a relay I have now resolved this Crank but no Fuel Pump issue with the help from all you guys above, many thanks.

 

Wow, did not know that! Thanks for sharing. Guess when turning on the key and hearing the pump run then shut off, was a false indicator of a pump running only on demand. Thanks for clearing that up for me!


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until the engine is running the pump has a timed start, when on it runs as there is no reservoir to maintain pressure IF THE PUMP RAN INTERMITTENTLY. woody