Dead fuel pump relay? - dead car!!

[Dr. Rog]

Originally Posted by RealEstate

Dr R, did you check out the FAQ?

EG see "Watch the tach carefully when a stall occurs. If it drops to 0 even before the engine winds down then that would indicate loss of ignition pulses to the coil negative terminal. Primary suspects would be the power stage or the crank position sensor. If tach tracks the engine speed as it winds down then that would indicate a fuel injection problem. Suspect radio supression relay or loss of fuel pressure due to relay or pump. "

Yes thanks I have been studying them.

When it was stalling I was making sure I wasn't crashing. The needle drops pretty quick anyhow so its difficult to discern a distinction. When it first lost power, 100 yards before cutting out dead it did not seem to be flickering. when it stopped all the lights came on and I had to make a hard left to get off the road.

Now it won't start, so it may be a different fault, or it may not.
The AA man said that "the feed to the coil wasn't switching". I think that is what is described above. If "Power stage" is "Ignition amplifier" (which it is in the Haynes manual.) then I have tried that so it looks again like the crank position sensor is the culprit.

It is a shame the on-board diagnosis unit was changed in these later cars. I see that "RPM sensor absent intermittently" is one of the listed codes.

I do have some issues with the FAQs. They are written very much on the basis of "if this try this" without a clear test to confirm the mall operation. I know this is how modern mechanics work but it does not help the budget motorist.

It is a shame the on-board diagnosis unit was changed in these later cars. I see that "RPM sensor absent intermittently" is one of the listed codes.

I have a probably faulty part, but I cannot find the text that says "put circuit tester across these terminals, do this and if ..then.."

[Steve940estate]

I think a lot of garages just swap bits until it works, some very kindly charge you for the new bits they try !
There are a few bits on here about making testers to check the fault codes on later cars but it doesn't help you get to work on Monday.
I'm very glad I have a slightly older car now with the code reader under the bonnet, it's all something to do with progress, isn't it.

[RealEstate]

I suggest you remove the crank sensor - easy to do, just one 10mm (IIRC) bolt. See if it is dirty eg covered in oil, inspect the cable for cracks etc. Check its resistance.

Then do a wiggle test of the engine bay wiring looms, wiggle cables & connectors, check earths. Worth looking at the fuel pressure regulator if you haven't done so; these can get v corroded.

[Dr. Rog]

Originally Posted by RealEstate

I suggest you remove the crank sensor - easy to do, just one 10mm (IIRC) bolt. See if it is dirty eg covered in oil, inspect the cable for cracks etc. Check its resistance.

Then do a wiggle test of the engine bay wiring looms, wiggle cables & connectors, check earths. Worth looking at the fuel pressure regulator if you haven't done so; these can get v corroded.

ooh there's a few new ones

What resistance should it be?? Which terminals should I read across??


I took the sensor out today, it was oily and dirty, no obvious damage, gave it a good clean with no effect.

An interesting job, it took a while to find it as it is well hidden under the pipes.

In the process I discovered the pipes thereabouts where perished and leaking.

What the h*** is that thing with an air pipe to it - it doesn't seem to be connected to anything (else) ???

A little TLC won't go amiss on any car, I might do a bit. Although I do find it deeply depressing as long as the *** car won't start.

[RealEstate]

Originally Posted by Dr. Rog

What resistance should it be?? Which terminals should I read across??

According to my wiring diag, crank sensor has 3 wires, Red, Black & SB(can't remember what colour this represents!), SB is the earth, so I would expect there to be resistance between the Red & black - sorry don't know what value, but not open circuit!

When you crank her over, do you get a spark? Do you hear the injectors tick?

When my car died completely, turned out to be the Fuel ECU - diagnosed by Bosch agent, but would think decent AA man should be able to diagnose that. Maybe you can borrow one for a test? I got a 2nd hand one off ebay & fitted Fred's chips.

[Dr. Rog]

Originally Posted by RealEstate

According to my wiring diag, crank sensor has 3 wires, Red, Black & SB(can't remember what colour this represents!), SB is the earth, so I would expect there to be resistance between the Red & black - sorry don't know what value, but not open circuit!

When you crank her over, do you get a spark? Do you hear the injectors tick?

When my car died completely, turned out to be the Fuel ECU - diagnosed by Bosch agent, but would think decent AA man should be able to diagnose that. Maybe you can borrow one for a test? I got a 2nd hand one off ebay & fitted Fred's chips.

I have a unit sealed both ends....I will investigate.
2nd AA man got no spark at one point, then decided the coil inlet was not switching.
Fuel ECU is an interesting one. I expect I have a spare from the old car, but like all those bits you cannot be sure it is not without fault.

There has been a slight delay whilst I resumed normal life, for the duration if a twinning ceremony and a special church service. Abnormal life will resume tomorrow. We have a lift to work but not one home

[Dr. Rog]

Originally Posted by RealEstate

I would expect there to be resistance between the Red & black - sorry don't know what value, but not open circuit!

Its a sealed moulded plug, each of the three pins is open circuit with each other.

Did I do that right??? It might be 400 ohm + Curses I shall have to try again

[Dr. Rog]

Originally Posted by Dr. Rog

Its a sealed moulded plug, each of the three pins is open circuit with each other.

Did I do that right??? It might be 400 ohm + Curses I shall have to try again

OK it does have some resistance, just rather a lot.
If we take the three terminals as A,B,C read right to left with the engraved "2" upright
AB=1.6 MegaOhm
AC=8.9 MegaOhm
BC=7.8 MegaOhm

I think I am measuring the insulation. This is as near open circuit as car electrics get in my experience of dodgy earths etc.

[RealEstate]

Those readings appear to be high.

Found this on the web:
http://www.youtube.com/watch?v=6ws8EVQ6NjE

https://wiki.bentleypublishers.com/d...specifications

Don't know if the mentioned 200-500 Ohms applies to our babies, but seems likely.

How about this one too !!
http://www.youtube.com/watch?v=064Il...1&feature=fvwp

[OldBlueVolvo]

Hi, the three wires to the impulse sensor are:-

1. Red (R)
2. Blue (BL)
3. Black (SB).

SB goes to ground as usual.

Specified resistance, between red and blue wires: 240Ω ±25.

This info is taken from a 740 manual but I believe that the information still applies to the 940. Someone can correct me otherwise. The FAQ gives a measured resistance value of 160Ω.
http://www.volvoclub.org.uk/faq/Engi...stition_Sensor
At least this gives a ball-park figure.