Car not starting

[dlewis]

Car decided not to start yesterday and the obvious fault is pump not priming but starter turning over.

Have been metering out a few things and swapped relays etc. This is what I know.

1. No supply to pump.
2. Continuity to pump earth side from battery earth.
3. Continuity to pump live side from fuel relay 87.
4. Live at main and fuel relays.
5. Direct 12v feed to pump does not fire it up.
6. Pump is only 14 months old.
7. Alarm/immombiliser appears to working.

Have looked in bible and the ECU wiring pdf and cannot seem to find the fuel pump fuse. Pretty sure it is not loose on the loom, 98 450.

Would anyone know where to find the fuse or suggest other cause?

[GreenV8S]

(5) seems significant, it implies that the problem is not just within the pump power supply. Does the pump run for a couple of seconds when you switch the ignition on?

[Johno]

Have you done any other work to the car ?

Double chck the inertia warning lamp isn't on as it would cause the same symptoms . .

[KENHIND]

The fuse is on the end of the loose wiring loom, red 10amp, same happened to mine, 400 Chim 1994, all exactly as you describe, fitted new fuse started immediatly.
Good luck.

KENHIND

[dlewis]

GreenV8S said:

(5) seems significant, it implies that the problem is not just within the pump power supply. Does the pump run for a couple of seconds when you switch the ignition on?

No, nothing from the pump having de-immobilised.

I am thinking that pump has blown the fuse and/or failed.

The only clicking seems to be from a relay on the fuseboard not the two loom relays, this may be symptomatic.

I plan to check fuse and get power back down to the pump having isolated it for now.

My loose loom seems to include a white unused connector, the LR fault code connector, a RISTS whatever that is for, a blue unused (card?) connector, four relays (incl main and fuel silver back) and two black connectors that appear to have loops fitted and paper tape around labelled 'harness OK' with part numbers whatever they are for.

So no fuses - I presume people mean simple in line radio type- surely it is not bound in to the loom wrap?

I have checked a lot of fuses on the board but none of these are supposedly for the pump anyway.

Edited by dlewis on Sunday 17th February 22:38

[dlewis]

Johno said:

Have you done any other work to the car ?

Double chck the inertia warning lamp isn't on as it would cause the same symptoms . .

Car was used last week and no electrical work since.

Fitted new braided brake hose to rear (having done fronts last weekend) but have double checked possibility of catching the wiring loom whilst jacking.
Presumably, the continuity would be lost anyway.

Yet to check this but assuming I have continuity to the pump this should be OK.

TBH I do not know where the warning light for this is.

Edited by dlewis on Sunday 17th February 22:44

Edited by dlewis on Sunday 17th February 22:53

[chimalsu]

try knocking the pump the contacts can stick,has worked for me in the past

[GreenV8S]

Your symptoms indicate that the ECU isn't driving the pump. This could be because the fuel pump circuit has failed (but if so, it would run when you hot-wired the pump unless you have two coincidental failures). You say the pump runs when powered direct. I'd just confirm that if you pull the fuel pump relay out and replace it with a link wire the pump does run. This proves that the rest of the circuit is OK and it's definitely just a problem at the ECU end. I think you already confirmed a good 12V supply on terminal 30 but if not I'd do that now. Also confirm that you have 12v on 85 or 86, and that the pump runs when you earth the other one (86 or 85). If that all checks out then you may have a failed ECU main supply (relay and fuse to check) or ECU hardware fault.

Edited by GreenV8S on Sunday 17th February 23:18

[dlewis]

GreenV8S said:

Your symptoms indicate that the ECU isn't driving the pump. This could be because the fuel pump circuit has failed (but if so, it would run when you hot-wired the pump unless you have two coincidental failures). You say the pump runs when powered direct. I'd just confirm that if you pull the fuel pump relay out and replace it with a link wire the pump does run. This proves that the rest of the circuit is OK and it's definitely just a problem at the ECU end. I think you already confirmed a good 12V supply on terminal 30 but if not I'd do that now. Also confirm that you have 12v on 85 or 86, and that the pump runs when you earth the other one (86 or 85). If that all checks out then you may have a failed ECU main supply (relay and fuse to check) or ECU hardware fault.

Edited by GreenV8S on Sunday 17th February 23:18

No, a direct feed to the isolated pump from a 12v transformer does not run the pump.

I have not tried a 'hot wire' at the relay, have yet to make up such a lead. Does this just jump the pin 30 to 87. Do you fuse it? Have been reluctant to do any bypassing until I find the fuse.

Voltage was on 30 at both relays. Will check the solenoid side tomorrow but recall that there was a circuit there just that I could not feel the ticking.

Does the ECU control the earth side? Just wonder why I have continuity from battery to pump.

[Steve_T]

David, could there be an earthing issue for the pump?

dlewis said:

GreenV8S said:

Your symptoms indicate that the ECU isn't driving the pump. This could be because the fuel pump circuit has failed (but if so, it would run when you hot-wired the pump unless you have two coincidental failures). You say the pump runs when powered direct. I'd just confirm that if you pull the fuel pump relay out and replace it with a link wire the pump does run. This proves that the rest of the circuit is OK and it's definitely just a problem at the ECU end. I think you already confirmed a good 12V supply on terminal 30 but if not I'd do that now. Also confirm that you have 12v on 85 or 86, and that the pump runs when you earth the other one (86 or 85). If that all checks out then you may have a failed ECU main supply (relay and fuse to check) or ECU hardware fault.

Edited by GreenV8S on Sunday 17th February 23:18

No, a direct feed to the isolated pump from a 12v transformer does not run the pump.

I have not tried a 'hot wire' at the relay, have yet to make up such a lead. Does this just jump the pin 30 to 87. Do you fuse it? Have been reluctant to do any bypassing until I find the fuse.

Voltage was on 30 at both relays. Will check the solenoid side tomorrow but recall that there was a circuit there just that I could not feel the ticking.

Does the ECU control the earth side? Just wonder why I have continuity from battery to pump.

[GreenV8S]

dlewis said:

No, a direct feed to the isolated pump from a 12v transformer does not run the pump.

I have not tried a 'hot wire' at the relay, have yet to make up such a lead. Does this just jump the pin 30 to 87. Do you fuse it? Have been reluctant to do any bypassing until I find the fuse.

Voltage was on 30 at both relays. Will check the solenoid side tomorrow but recall that there was a circuit there just that I could not feel the ticking.

Does the ECU control the earth side? Just wonder why I have continuity from battery to pump.

I may have made a wrong assumption about what you've done then.

The pump -ve is permanently earthed. I think you have already done a continuity test to battery -ve. If you now connect the pump +ve to battery +ve (via a fused wire) the pump should run. If not, you need a new pump. I don't know what the transformer output characteristics are but I wouldn't count on it being able to run the pump so that test doesn't tell me anything.

If the pump does run direct from the battery then you need to work back through the power supply to see why it isn't getting 12V.

Something to bear in mind while you're doing this is that the ECU only runs the pump for a couple of seconds after you switch the ignition on, and while the engine is turning. So if you're chasing voltages through you need to get set up and then flick the ignition on.

[dlewis]

Steve

I have tried to check for this, I think the ECU provides the earth not the chassis etc.

I did have continuity from battery terminal to pump neg. wire but not entirely sure how it gets it.

Dave

[dlewis]

GreenV8S said:

dlewis said:

No, a direct feed to the isolated pump from a 12v transformer does not run the pump.

I have not tried a 'hot wire' at the relay, have yet to make up such a lead. Does this just jump the pin 30 to 87. Do you fuse it? Have been reluctant to do any bypassing until I find the fuse.

Voltage was on 30 at both relays. Will check the solenoid side tomorrow but recall that there was a circuit there just that I could not feel the ticking.

Does the ECU control the earth side? Just wonder why I have continuity from battery to pump.

I may have made a wrong assumption about what you've done then.

The pump -ve is permanently earthed. I think you have already done a continuity test to battery -ve. If you now connect the pump +ve to battery +ve (via a fused wire) the pump should run. If not, you need a new pump. I don't know what the transformer output characteristics are but I wouldn't count on it being able to run the pump so that test doesn't tell me anything.

If the pump does run direct from the battery then you need to work back through the power supply to see why it isn't getting 12V.

Something to bear in mind while you're doing this is that the ECU only runs the pump for a couple of seconds after you switch the ignition on, and while the engine is turning. So if you're chasing voltages through you need to get set up and then flick the ignition on.

Yes, I did notice a large voltage drop when I fed the punp direct so it may not be duff.

Will use the battery to feed it direct (with a fuse) next.

If there is a permanent earth does that implies the ECU is controlling the live.

I want to trace the live but need help in finding the fuse.

Thanks for your patience.

Dave

[GreenV8S]

dlewis said:

not entirely sure how it gets it.

The fuel pump relay has a permanent 12V supply on pin 30 and switched ignition feed to 85 (or maybe 86, I forget). The ECU pulls 86 (or 85) to 0v to close the relay. When the relay is closed, it connects 30 to 87a. 87a is wired to pump +ve via the inertia cut-off switch. The pump -ve is permanently earthed to the chassis. The relay is a twin pole relay and the second pole powers the lambda sensor heaters (if fitted).

[dlewis]

GreenV8S said:

dlewis said:

not entirely sure how it gets it.

The fuel pump relay has a permanent 12V supply on pin 30 and switched ignition feed to 85 (or maybe 86, I forget). The ECU pulls 86 (or 85) to 0v to close the relay. When the relay is closed, it connects 30 to 87a. 87a is wired to pump +ve via the inertia cut-off switch. The pump -ve is permanently earthed to the chassis. The relay is a twin pole relay and the second pole powers the lambda sensor heaters (if fitted).

According to the ECU wiring pdf pin 86 is the ignition feed so 85 must be controlled by the ECU to close the solenoid.

I admit to getting confused between earth on chassis and hard wired earths, in that it appears the pump is a wired earth although it grounds to the chassis with what must be a suppressor.

[Cider Andy]

dlewis said:

2. Continuity to pump earth side from battery earth.
5. Direct 12v feed to pump does not fire it up.

This would suggest the pump has failed. Substitute a 12V lamp for the pump, using the pump connections. See if this lights for a second or so at ignition on (with the immobiliser disarmed).

[blitzracing]

If this is anything like the Ginetta pumps, a trace of dirt can get between the rotors, and they just stop. Trick is to get a 12volt supply, and wire the two pump connections in reverse (disconnect from the TVR loom first), to make the pump spin backwards. This can kick the dirt back out. Mine runs fine on a 12 volt battery charger, and you can see if its drawing a few amps as it should.

Mark

[dlewis]

OK, pump running on more powerful direct feed.

Looks like it may be a ECU fault as has been suggested.

Have made up a fused lead tonight and will reconnect pump and do a hot wire tomorrow evening, then look for the fault.

Been a tadge cold tonight in the garage so did other things.

Many thanks for your comments to date.

[dlewis]

Eureka, just reconnected the pump and put the ECU back on to the loom and hey presto she fired up!!!!!!!!

I have had the ECU in house overnight, lightly rubbed the pins and had a peak inside but found nothing out of place and all chips are soldered.

I had previously disconnected and reconnected the loom plug in case of a pin connection fault.

Had to go round the block, so pleased it is resolved.

Will think about what it could have been but main suspect is control of the fuel relay.

Thanks GreenV8S et al.