Thursday, October 07, 2010 - 02:49 pm, by: Malcolm Hall(Neddy)
Hi Folks. My V8 is still bringing a smile to my dial after 6 years of use as my daily driver but in recent days she has let me down 4 times. Symptoms: cold start and running OK but not starting due to no power to fuel pump when hot sometimes. Tried the +B -> FP link in the diagnostics port, no go - not surprising as during the fault condition there is no voltage at the +B connector there when cranking. Checked the main EFI relay operation during fault condition and all measures up OK. I think that the +B signal starts at this relay and should appear at the diagnostic port, the fuel pump ECU and the ECM but seems to be absent. The problem is complicated by the fact that it is so intermittent (all working fine now, for instance). Do these symptoms suggest anything to anybody?
I can get the motor running again by running a direct lead from the battery +ve to the FP connector in the diagnostics port but I'm not happy about driving round like that - apart from the pump not liking a full 12V long-term, if I have an accident the pump might keep on running and cause a bit of havoc... Any suggestions about what to try next would be welcome!
Friday, October 08, 2010 - 09:02 am, by: Christian Molenda(Christof)
You have 2 issues there.. The Fuel pump ECU is one problem, The other is the fact there is no 12v at the B+ terminal in the Diagnostics port. Either way replace the Fuel pump ecu and your problem is solved. The B+ is only in the port for diagnostic reasons.
Friday, October 08, 2010 - 09:55 am, by: Tom Richards(Tomr)
i had the same problem on my sons V8.
i swapped some of the relays around in the relay box on the lhs of the engine but that didnt fix it
I found by "shaking" on of the relay cans, you would hear relays clinking in (12v would appear at B+) and the car would then start. this happened occasionly for a while and then the fault dissapeared.
I cannot give you the exact relay off the top of my head, but it was one of the real prominent ones
Friday, October 08, 2010 - 04:34 pm, by: Malcolm Hall(Neddy)
Thanks for the suggestions folks. I am thinking that a faulty fuel pump ECU might the reason for the lack of +B signal when it's dead as the output from the main EFI relay does go there. I will check the wiring as a precaution, but the fault is not present now so it's hard to tell. I will invest in a new ECU anyway and see what happens.
Wednesday, October 20, 2010 - 03:46 pm, by: Malcolm Hall(Neddy)
Update: I replaced the fuel pump ECU and the fault re-appeared the following day, so not that (I now have a spare if anybody would like to buy it!). I got home with a jump lead from the battery to "FP" in the diagnostic port but once again, during the fault condition there was no "+B" signal in the diagnostic port. I have now made myself up a set of extension leads so that I can operate the main EFI relay outside the fuse box and check for signals on it the next time the fault occurs - the "+B" is an output signal from that relay. Obviously Sod's Law means that the fault has not shown itself since I set this up but when it does, I'll be ready for it. I'll keep you posted because what I find might save somebody else from spending $300 on an ECU that is in fact OK. My thinking at the moment is that either the relay itself is getting tired or maybe the fuse feeding it has an intermittent open circuit, but it could be that the signal that pulls the relay in ("M-REL") is missing and this might indicate a fault in the ECM or wiring from it. Any bets on how long it will be before I see the problem again?
Wednesday, October 20, 2010 - 07:43 pm, by: Tom Richards(Tomr)
hi malcolm, as a wrote above, i tracked it back to the relay the B+ goes thru. It does not energise but i could get it to energise by moving it around. I didnt have a full cct diag to go further, but as with yours it was intermittent. Maybe a dry joint on the relay base, but more likely a fault at the source of the signal to energise the relay. Maybe that is in the main ECU.
Thursday, October 21, 2010 - 12:53 am, by: Malcolm Hall(Neddy)
Hi Tom - we're on the same wavelength here, but I want to know which of the following problems is at the root of the trouble:
a) no signal to energise the relay (this is the "M-REL" signal from the ECM)
b) no 12V supply to the relay contacts (this comes from the fuse right next to the relay, so a poor connection in the base somewhere probably)
c) dodgy relay contacts, so the relay is supplied OK, it pulls in OK but doesn't pass current across the contacts to the output.
Until it happens again I can't tell which but after nearly 20 years of use, the chances are it's the last option and a new relay will fix it. I'll repost when I have it sussed.
Thursday, October 21, 2010 - 12:08 pm, by: Malcolm Hall(Neddy)
Hi Tom - this is the schematic that I am working to. That energise signal (M-REL) comes straight from the ECM so if it was low voltage during fault either the ECM itself is a problem or there's a fault in the wiring somewhere between that module and the relay... If I find the same problem (when it next appears...) I'll be checking the voltage sent out from the ECM as the next step.
Cheers Malcolm
Frank Csapo Tinkerer NSW Volvo 244GLE with 1JZ-GTE
Sunday, December 26, 2010 - 05:49 pm, by: Andy Losurdo(Funny_guy77syd)
ok might sound like a dumb qestion i have similar problem but in my case my car dies every so often as i drive it i replaced fuel pump but same problem is fuel pump ecu and puel pump relay same thing and im driving a 32 any info would be gladly apreciated