Omega Owners Forum
Omega Help Area => Omega General Help => Topic started by: terry paget on 04 December 2013, 16:21:49
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X84GNB 2000 2.5 petrol manual estate
Engine cranks well but does not start. My first thought was failed crank sensor. Then I loosened a fuel pipe to check fuel feed when cranking, and found there was none. There is fuel in the tank.
I know there is a relay, but do not know where. Is there a fuse? Perhaps the pump has failed.
Please advise procedure to isolate fault.
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fuse 18, 20amp. in dash. ;)
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Give the tank a kick from under the bumper whilst a willing assistant cranks it :y
Pumps stick when they start to fail...
Other thing is to swap the two purple relays in the engine bay fuse box with ones from a working car :y
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Iirc the fuel pump wont pump fuel if the crank sensor has died.
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Iirc the fuel pump wont pump fuel if the crank sensor has died.
It runs briefly at position 2 to prime the fuel rail. If the engine fires, then it starts and runs permanently...
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Thanks Gentlemen. I have checked Fuse 18, it's OK. I have pulled out the two purple relays, but could not get both purple relays out of R706FHD, a 2.0 petrol. I got one out, I have more at work so will bring them home tomorrow.
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dont know if important or not but check the terminals are the same on the relays you exchange---my miggy had 1 more pin on its relay than on the relay i got from another miggy---wierd
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Iirc the fuel pump wont pump fuel if the crank sensor has died.
It runs briefly at position 2 to prime the fuel rail. If the engine fires, then it starts and runs permanently...
I always believed the fuel pump operated at low rpm as long as the starter was cranking, but not with just the ignition switched. This presumably was a safety measure to avoid fuel fires after accidents. I did expect fuel to feed while I cranked the starter. It did not happen.
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Iirc the fuel pump wont pump fuel if the crank sensor has died.
It runs briefly at position 2 to prime the fuel rail. If the engine fires, then it starts and runs permanently...
Could this be linked to crank sensor.... in college we observed a mondeo that had a faulty crank sensor. we checked for spark during cranking and there was no spark. this is apparently indicative of a failed crank sensor. if it has no spark is something somewhere cutting the fuel off as precaution??? just a thought :)
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Iirc the fuel pump wont pump fuel if the crank sensor has died.
It runs briefly at position 2 to prime the fuel rail. If the engine fires, then it starts and runs permanently...
Could this be linked to crank sensor.... in college we observed a mondeo that had a faulty crank sensor. we checked for spark during cranking and there was no spark. this is apparently indicative of a failed crank sensor. if it has no spark is something somewhere cutting the fuel off as precaution??? just a thought :)
As said above, I see the wisdom of cutting off fuel supply below, say, 200rpm, to minimise fire risk. But engine will never start unless fuel pressure is raised while cranking to start engine, therefore pump relay is engaged with starter relay.
Today I shall substitute good violet relays for the two in X84GNB. IF no change, I suppose i should next check volts and action at the fuel pump.
I have had five non starter Omegas, all caused by failed crank sensors. I did not note down that I had checked fuel feed on those occasions, but I think I would have.
Does anyone know which colour wires to fuel pump and gauge socket are power to the pump?
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I think pump feed is blue/red (or is it red/blue)?
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..and I don't recall a priming pulse either (had fun trying to get my X30XE running from empty and a dead crank sensor); manually jumpered the fuel pump relay to get fuel up to the rail.
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If no joy with the relays, give the tank a kick about a foot in from the towing eye whilst some one else cranks it :y
If it fires, the pump is on its way out...
Quicker and easier than testing for a wiring fault... might as well start with the easy stuff :y
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In all the years I have worked on them, I have never seen a priming pulse on the 2.5/3.0, the fuel relay only pulls in when the crank shaft is seen to turn.
Reality is that the fuel pressure remains for days and even weeks after the engine is turned off (unless you have a leaky injector) so no need for it.
Hence crank sensor is a favourite.
An option is to pop the top off the fuel pump relay and manualy actuate the relay if you must, do you have a spark?
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Reality is that the fuel pressure remains for days and even weeks after the engine is turned off (unless you have a leaky injector) so no need for it.
In my case I'm not using the Omega pump (or tank) - one from a Ford Focus of unknown heritage and I think Fords DO have a priming pulse..perhaps as their pump setup isn't as good?
Not helping the OP's problem though ;D
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Got a spare pump and crank sensor knocking about cheap if needed ;)
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Thanks chaps. Today I fitted two good violet relays, GM90 494 959, cranked engine, did not start. Had wife crank engine while I thumped centre of tank with plastic mallet (found it hard to kick there) but, in vain. did not start. All worth trying, thanks for tips. I am out tomorrow, using OE03EWW, 3.2 with slipping clutch, but will renew investigation Saturday. I shall test volts on wires to pump on cranking and report back. Any new suggestions, please keep them coming.
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Crank sensor it is then :y
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Crank sensor it is then :y
I hope you are right. Al. I have changed five in the past, it is a simple job, However, my memory is that when a V6 Omega refuses to start, but cranks vigorously, the first thing I check is fuel feed by loosening the feed hose and cranking. If fuel spurts out, the fault lies elsewhere, almost certainly crank position sensor. In this case, fuel did not spurt out. So I suspect fuel feed failure.
Senators were devils to start in the winter if they had more than five days without use. The distributor right at the front behind the cheese grater grill got damp, then it would either not start at all, or start on two or three, and take quite a long run to dry everything out. Omegas are much better, with coil packs at the rear of the engine and no distributors.
I will keep in touch. I shall check there are 12 volts to the pump when cranking, if there are not I shall bring 12 volts to it. If there are 12 volts to it and it pumps, then it must be crank sensor.
I have not checked for spark at plug. I suppose I could take a lead off, put a spare plug in it, lay it on the head and crank engine. No spark would confirm crank sensor fault. Spark would suggest dead pump.
Any thoughts?
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You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on :-\
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You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on :-\
With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.
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The engine will run for about 5 seconds with the contents of the fuel rail :y
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You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on :-\
With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.
Its not, its activated along with the spark and injectors once a valid crank pulse is seen (hence why we see miss diag sometimes as when the crank sensor fails people rush off checking the fuel pump relay and fuel pump as there is no fuel to rail).
Fuel pump is under ECU control
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You're unlikely to find voltage at the pump without the engine running, based on Marks' suggestion that it doesn't prime when the ignition is switched on :-\
With just the ignition on, no. But with the starter cranking, yes . Otherwise the poor thing has no chance of starting. I believe the fuel pump relay is activated by the starter relay circuitry. Once the engine starts the crank signal sensor holds it in.
Its not, its activated along with the spark and injectors once a valid crank pulse is seen (hence why we see miss diag sometimes as when the crank sensor fails people rush off checking the fuel pump relay and fuel pump as there is no fuel to rail).
Fuel pump is under ECU control
Thanks Fuse 18. Just to get this straight, fuel pump relay is actuated by the ECU when it gets valid crank sensor pulses and by nothing else. Thus, with ignition on, engine still, no pulses, no volts to pump. But with starter cranking engine we get crank sensor pulses, which trigger volts to pump.
So if I check spark at plug lead when cranking and find one, crank sensor is OK, fault must lie in pump (or leads to it). If I get no spark, crank sensor is dead.
Please confirm.
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Sounds a logical assumption to me.
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From memory, K43 is the injection system relay that supplies the pos volts for the injectors (plus some of the vac actuators) and is ECU controlled, this switched pos feed from K43 then turns the fuel pump relay on (K44).
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You were all right and I was wrong. Found no spark this morning. So it's crank sensor. It's a 2.5 so model is it's critical that I replace with original fitment, which is labelled GM 90462061. Have you got one, Omegod?
Thanks for your help chaps, saved me wasting my time playing with the fuel pump.