No fuel pump prime
Discussion
98 4.0l recently started cutting out whilst in motion. Would restart again immediately until…the last occasion there was no fuel pump priming to be heard. Breakdown truck got me home. For the past week I have, I think, looked everywhere for the fault. No luck…I’m stuck. Help please. A remote battery proved the pump still works, fuses are good, ECU and fuel pump relays replaced, inertia switch not activated, new ignition module fitted, cables in the B column seem good, immobiliser bypass completed a year ago…Disconnected the battery to try and reset the ECU…Battery is new and the car is on a trickle charge when in the garage. Have I missed something? Can someone put me out of my misery please?
I’d check the wiring first, especially the connections to the pump which can become corroded.
If you have a test lamp check at the inertia switch with ignition on, you should see a good 12 volts at the yellow wire, if it’s good here then it goes through multiple connectors before the pump so I’d suspect these.
Could also be ecu related but I’d rule the above out first.
You could do a temp bypass of the wiring from inertia switch to pump for test purposes, don’t overlook a faulty ground either.
If you have a test lamp check at the inertia switch with ignition on, you should see a good 12 volts at the yellow wire, if it’s good here then it goes through multiple connectors before the pump so I’d suspect these.
Could also be ecu related but I’d rule the above out first.
You could do a temp bypass of the wiring from inertia switch to pump for test purposes, don’t overlook a faulty ground either.
Edited by Belle427 on Sunday 10th July 08:30
When I had this it was a failed meta immobiliser. I used http://www.tvruk.tv/ Carl Baker for advice and the solution.
Was the immobiliser bypass only of the starter solenoid circuit? This is the commonest failure and I had to do the same on the Meta immobiliser on both a previous Chimaera and my current Griff. But it also isolates the ECU / fuel pump.
8 months later it cut out on me twice whilst driving along, once at 60 mph! Recycling locking / unlocking the car got me going again. Replacing the alarm and immobiliser sorted it out in the end.
I think there have been other threads recently about Meta immobilisers causing cars to stall in addition to the failure to turn over but I can't seem to find them.
8 months later it cut out on me twice whilst driving along, once at 60 mph! Recycling locking / unlocking the car got me going again. Replacing the alarm and immobiliser sorted it out in the end.
I think there have been other threads recently about Meta immobilisers causing cars to stall in addition to the failure to turn over but I can't seem to find them.
Assuming that your imobiliser has not failed on the ignition circuit ,as said above it is likely to be in one of the multiway plugs.
The worst offender is the multi connector behind the passenger B post as it very often gets damp here. It is worth a quick check to clean its contacts.
If this does not cure the problem I can give you a schematic of the Immobiliser wiring for you to trace the fault.
Best of luck!
The worst offender is the multi connector behind the passenger B post as it very often gets damp here. It is worth a quick check to clean its contacts.
If this does not cure the problem I can give you a schematic of the Immobiliser wiring for you to trace the fault.
Best of luck!
Thanks for the replies… I have checked and cleaned the spade contacts on the fuel pump. The connectors in the B pillar have been checked and cleaned. Strangely enough it seems that the cable to the petrol pump (yellow) is not via a connector. It appears that a piece of cable has been spliced in so the cable runs straight through…? How do I bypass the inertia switch?
The infamous PH TVR Chimaera owner ChimpOnGas posted a very helpful reply to someone with similar problems, the information that he posted might be of some use to you
The most important thing to follow is the use of a multimeter as it is only voltages or the lack of them that will point you in the right direction for finding the cause of the failure
Below is the ChimpOnGas post and a link to the topic as there is much more info posted to it
https://www.pistonheads.com/gassing/topic.asp?h=0&...
The most important thing to follow is the use of a multimeter as it is only voltages or the lack of them that will point you in the right direction for finding the cause of the failure
Below is the ChimpOnGas post and a link to the topic as there is much more info posted to it
https://www.pistonheads.com/gassing/topic.asp?h=0&...
ChimpOnGas said:
I was always taught... "You can't fix something until you understand how it works" 
Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Keep in mind the immobiliser is just a switch, one you turn on & off with your fob from a distance, but a switch all the same.
Actually it's two switches.
One switch opens the circuit to the starter solenoid, so when you turn the key to the sprung start position you can crank the engine.
The second switch turns on the ECU, and its actually the ECU that turns the fuel pump on not the immobiliser but clearly it's all linked in a chain if you like.
The ECU will only turn the fuel pump on for three seconds when you turn the ignition on. After three seconds the ECU turns the fuel pump off because obviously you don't need a flow of fuel until the engine is running, the three second pulse is just designed to prime the fuel rail in preparation for the start.
The ECU wont turn the pump back on again until it either sees an RPM signal from the distributor indicating cranking, or you turn the ignition off & back on again.
Relays are just electromechanical switches (mini solenoids if you like) that allows a low amp feed to switch on a high amp circuit, they are used to protect low amp switch contacts that wouldn't ordinary cope with the higher amp demands of components like fuel pumps, starter motor solenoids, headlights, horns ect ect.
The ECU has a relay and the ECU activates the second relay on the fuel pump circuit, if your fuel pump relay is faulty obviously the fuel pump wont run, if you then put that faulty fuel pump relay in the ECU relay socket the ECU wont switch on. And because the ECU isn't live it can't turn the fuel pump on.
So you see, the often promoted practice of swapping the two relays around is the answer to nothing other than further confusion!
The truth is the problem may be a relay, or it may reside inside the immobiliser which itself houses two small low amp switching relays, one for each of the two circuits it controls (ECU & Stater Motor Solenoid).
So how do you know where the problem really is without blindly replacing things at great cost in the hope you might stumble on the solution?
Well here's a clue....
Topper04 said:
Thanks for the replies… I have checked and cleaned the spade contacts on the fuel pump. The connectors in the B pillar have been checked and cleaned. Strangely enough it seems that the cable to the petrol pump (yellow) is not via a connector. It appears that a piece of cable has been spliced in so the cable runs straight through…? How do I bypass the inertia switch?
Very rarely these fail but you would normally join the yellow and black cable to the yellow one if the colours are oem.Thanks for the replies… I have checked and cleaned the spade contacts on the fuel pump. The connectors in the B pillar have been checked and cleaned. Strangely enough it seems that the cable to the petrol pump (yellow) is not via a connector. It appears that a piece of cable has been spliced in so the cable runs straight through…? How do I bypass the inertia switch?
Topper04 said:
98 4.0l recently started cutting out whilst in motion. Would restart again immediately until…the last occasion there was no fuel pump priming to be heard. Breakdown truck got me home. For the past week I have, I think, looked everywhere for the fault. No luck…I’m stuck. Help please. A remote battery proved the pump still works, fuses are good, ECU and fuel pump relays replaced, inertia switch not activated, new ignition module fitted, cables in the B column seem good, immobiliser bypass completed a year ago…Disconnected the battery to try and reset the ECU…Battery is new and the car is on a trickle charge when in the garage. Have I missed something? Can someone put me out of my misery please?
I had exactly the same symptoms earlier this year. While I waited at the side of the road for the RAC, I messed around and realised the fuel pump wasn’t priming. Tried the usuals mentioned here and I had spare fuel pump relay to try too. Nothing. I then remembered the 6.8kOhm resistors in the ignition amp circuit had a bearing on the signal going back to the ECU. These are those short black blocks. I remade those connections by removing and reinserting a few times and then I heard the fuel pump prime again with the ignition on. That got me going, I cancelled the call-out and drove home ok. My resistor connections were heavily corroded.
Have a read here- it shows the resistor.
http://www.britishv8.org/Articles/Rover-14CUX-EFI....
It may be taped inside the loom if you cant find it
Normally the pulses from the coil /ignition amp tell the ECU the engine is turning to turn on the fuel pump. I have always assumed that applying power to the coil when ignition is turned on also sends a pulse through the resistor, as opposed to simply putting 12v on the ECU, but I've not tried a power on with the resistor disconnected to check this.
If you can borrow RoverGauge from someone it shows the fuel pump activation from the ECU point of view and you can use RoverGauge to turn the pump on full time to troubleshoot.
Without RoverGauge:
You should hear the relays click in the foot well as you turn on the ignition (dont start)
Power on- 2 relays close. Main relay and pump relay. About 3 seconds later the fuel pump relay should drop out with a click as the engine is not running,
If this is working then the fault is not the ECU , fuel pump relay, resistor, or coil trigger (?).
http://www.britishv8.org/Articles/Rover-14CUX-EFI....
It may be taped inside the loom if you cant find it
Normally the pulses from the coil /ignition amp tell the ECU the engine is turning to turn on the fuel pump. I have always assumed that applying power to the coil when ignition is turned on also sends a pulse through the resistor, as opposed to simply putting 12v on the ECU, but I've not tried a power on with the resistor disconnected to check this.
If you can borrow RoverGauge from someone it shows the fuel pump activation from the ECU point of view and you can use RoverGauge to turn the pump on full time to troubleshoot.
Without RoverGauge:
You should hear the relays click in the foot well as you turn on the ignition (dont start)
Power on- 2 relays close. Main relay and pump relay. About 3 seconds later the fuel pump relay should drop out with a click as the engine is not running,
If this is working then the fault is not the ECU , fuel pump relay, resistor, or coil trigger (?).
I have to say that re-reading your original post, your fault does sound like a bad connection somewhere.
The only similar things I have had that caused sudden non-starting were:
Car stalled at a roundabout and wouldn't restart - no prime either. I called my TVR guru who suggested simply locking and unlocking the car. Bingo.
The other time, I had driven half a mile from home, turned a corner and coasted to a halt, engine not running.
RAC called, he came and tested what he could, and was pretty certain it was fuel pump related. However, he was not allowed to test fuel pressure at the rail, so had to admit defeat. He suggested relaying the car 80 miles to my TVR expert, but I had my own trailer so went and fetched it.
Next morning I arrived at the TVR expert with the car on the trailer and every even vaguely relevant spare part I owned in the boot.
He spent about 20 minutes testing logically and said "It must be the ECU - and I don't have a spare".
I reached into the boot and pulled out a spare that I had bought in a job lot.
Not the right ECU chip, but still a spare ECU.
He swapped the ECUs over and it started immediately.
Next job was to extract my correctly mapped chip from the duff ECU and put it in the working one, at which point we found that the bottom edge of the circuit board was corroded with acid residue exactly where the fuel pump chip was. I had had a battery boil slightly about 2 years previously, and it had taken that long to cause a problem. So don't store your ECU on the carpet alongside the battery, as that area can also get wet.
The only similar things I have had that caused sudden non-starting were:
Car stalled at a roundabout and wouldn't restart - no prime either. I called my TVR guru who suggested simply locking and unlocking the car. Bingo.
The other time, I had driven half a mile from home, turned a corner and coasted to a halt, engine not running.
RAC called, he came and tested what he could, and was pretty certain it was fuel pump related. However, he was not allowed to test fuel pressure at the rail, so had to admit defeat. He suggested relaying the car 80 miles to my TVR expert, but I had my own trailer so went and fetched it.
Next morning I arrived at the TVR expert with the car on the trailer and every even vaguely relevant spare part I owned in the boot.
He spent about 20 minutes testing logically and said "It must be the ECU - and I don't have a spare".
I reached into the boot and pulled out a spare that I had bought in a job lot.
Not the right ECU chip, but still a spare ECU.
He swapped the ECUs over and it started immediately.
Next job was to extract my correctly mapped chip from the duff ECU and put it in the working one, at which point we found that the bottom edge of the circuit board was corroded with acid residue exactly where the fuel pump chip was. I had had a battery boil slightly about 2 years previously, and it had taken that long to cause a problem. So don't store your ECU on the carpet alongside the battery, as that area can also get wet.
An update chaps…Upon installing 2new relays the fuel pump primed for 3 seconds. Turned the key but no ignition. A multimeter showed that no volts were getting to the coil. Engine turned over but no ignition obviously. So, a new Bosch coil, dizzy cap, ignition module and cleaned resistors later and….no fuel pump prime. Suggestions on a postcard please. A year ago the immobilser to starter motor was pypassed, so it’s now looking like it is not talking to the ECU and not telling it to switch on the fuel injectors. Sound about right? I was hoping to find someone in the Grimsby area that may have a similar car ( 4.0l serp engine ) that would allow me to plug in my ECU unit just to see if the engine would fire up…any takers? Finally…how difficult is it to completely cut out the immobiliser? Thanks in advance…
I believe a standard fitted immobiliser does not cut the ignition coil so I’d try and verify that side of things first.
The coil is fed from fuse 12 via the ignition switch, are you testing coil positive to a known good ground?
If power is missing here then my thoughts are the ecu isn’t getting the run signal to trigger the fuel pump.
The coil is fed from fuse 12 via the ignition switch, are you testing coil positive to a known good ground?
If power is missing here then my thoughts are the ecu isn’t getting the run signal to trigger the fuel pump.
Just one word of caution when testing voltages.
A 12v reading on its own doesn't necessarily mean that all is well. You must also figure in current sufficiency.
Let me explain.....
My reversing light would not work. Obvs, first think to check was the bulb - that was good (tested elsewhere and it lit)
So then suspected the reversing light switch on g/box. Ign on, jammed it in reverse, bingo 12v appears the RL loom, but light did not light!
So bad earth? Nope! full continuity there.
Weird, huh? I don't know why, but I then took a 5w panel light holder and bulb and held the wires to the original 21w RL bulb holder and the bulb lit.
Now I'm totally flummoxed!
Turns out that unusually, the RL switch on a TVR switches live and not earth. It was switching well enough to supply 12v to the bulb and enough current to light a 5w bulb, but not a 21w RL bulb.
Changed RL switch and the world was bright again!!
So contacts/connectors can appear to be good and show a 12v supply, but not sufficiently robust that they can supply the required current.
A 12v reading on its own doesn't necessarily mean that all is well. You must also figure in current sufficiency.
Let me explain.....
My reversing light would not work. Obvs, first think to check was the bulb - that was good (tested elsewhere and it lit)
So then suspected the reversing light switch on g/box. Ign on, jammed it in reverse, bingo 12v appears the RL loom, but light did not light!
So bad earth? Nope! full continuity there.
Weird, huh? I don't know why, but I then took a 5w panel light holder and bulb and held the wires to the original 21w RL bulb holder and the bulb lit.
Now I'm totally flummoxed!
Turns out that unusually, the RL switch on a TVR switches live and not earth. It was switching well enough to supply 12v to the bulb and enough current to light a 5w bulb, but not a 21w RL bulb.
Changed RL switch and the world was bright again!!
So contacts/connectors can appear to be good and show a 12v supply, but not sufficiently robust that they can supply the required current.
Edited by Harry Flatters on Friday 29th July 12:31
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