Air Flow Meter pics for Chris (Truckarms)

[TonyN]

Hes a couple of pics of you problem, dunno there are clear enough to see much, but here goes.

A re-cap for the nosey people who will look as well

Problem...Truck starts just fine, then dies 1-2 secs after starting. Will always start, but never runs, (keeping the key to crank keeps it running, but ruins starter motor)

Troubleshoot... bypass pump relay by jumping connections in Diagnostic box, so pump getting 12V all the time ignition is on. Truck runs fine, ruling out fuel pump/filter/pressure issues.

Answer... Open Circuit Relay (or fuel pump relay) not holding open when ignition key in On mode, but OK when cranking.

Fixing... The 'run' coil of the OCR gets it feed from the Air Flow Meter (a -ve to complete the circuit) Most place would have said "AFM is bust, that £200 for a new one please!" But I popped the lid off to have a look inside and found some interesting sights.

The circled bit (Connection E1 )in pic one is bent, a long way to the left, so the needle on the swipe arm is hitting it, and not going all the way over. When the motor is running (pic 3) the arm is out the way, and E1 should touch the long silver bit (connection Fc )on its right completing a circuit to the OCR. With E1 bent, Fc cannot touch E1, so the OCR 'run' coil wasn't being activated. With E1 bent back as in pic 2 you can see the sweep arm all the way over, and holding Fc off of E1 while the key is is start mode, and the OCR is powered from the starter motor relay.







Also, when checking the rest of the AFM, the temperature correction sensor dosn't seen to be working, so the truck dosn't know if its the middle of winter or the middle of summer, so while its running fine, it could run better in theory, so I'd keep an eye on Ebay for a used AFM still.

[Vagrant No2]

I would agree with that dianoisis , well done son .
I did say I thought it maybe a lost constant feed to pump , somewhere .

[truckarms]

10 out of 10
Thank you very much

I can now get the christmas tree!!!!!

[Diezel Weazel]

Well done & well spotted that Man

There's always a Payback.... You just can't see the problem Coming !!!!
We have a Man that sorts em tho !!!!!!!!!!

[truckarms]

Hi Tony,
Thanks for the help last night, once started it drove home fine and I checked everything, (relay, the above and everything seemed fine) This morning car started first time, must just have been some dust or water somewhere, that or the pump is on the way out (I hope not so will keep the service slot for another few days and let you know the progress.

For the rest of you,
I left work last night and drove 5mins up the road to Wickes.
Went bought some bits and came back to the car which would not start, engine cranked but no fuel.
First tried to call the RAC but I think they were a little busy yesterday and so after 10mins I gave up and started trying things like what was talked about above. after taking it all apart everything looked ok so phoned the 24hr TONY help line, who was as ever very helpful and talked me through a few things and we managed to start the car using the paperclip in the diagnostic port. so I drove home. Thats a slab of beer or something for you tony thanks!

So I checked everything at home and cant find any problems but am worried that it might just be the fuel pump. Because I have been running on LPG the pump just pumps pertrol round 24/7 under full load which cant do it any good, does anyone have a system which turns off the fuel pump when you are on LPG?

Cheers

[dieselboy]

Hi Tony,
Thanks for the help last night, once started it drove home fine and I checked everything, (relay, the above and everything seemed fine) This morning car started first time, must just have been some dust or water somewhere, that or the pump is on the way out (I hope not so will keep the service slot for another few days and let you know the progress.

For the rest of you,
I left work last night and drove 5mins up the road to Wickes.
Went bought some bits and came back to the car which would not start, engine cranked but no fuel.
First tried to call the RAC but I think they were a little busy yesterday and so after 10mins I gave up and started trying things like what was talked about above. after taking it all apart everything looked ok so phoned the 24hr TONY help line, who was as ever very helpful and talked me through a few things and we managed to start the car using the paperclip in the diagnostic port. so I drove home. Thats a slab of beer or something for you tony thanks!

So I checked everything at home and cant find any problems but am worried that it might just be the fuel pump. Because I have been running on LPG the pump just pumps pertrol round 24/7 under full load which cant do it any good, does anyone have a system which turns off the fuel pump when you are on LPG?

Cheers

what would be good is some sort of clutch like how air conditioning dis-engages when its off...
just a thought

[truckarms]

That would be nice if it was a manual pump but the pump is in the tank and is electric so dont know if a clutch would work,
I was thinking of a pressure release return hose, i.e. when you dont have the injectors working the pressure release circuit opens and then the pump is not working under load. but I think that would be over complicated. I also thought of a solenoid that just stops the pump but then every time the engine flicks back to petrol it would stall. I cant find much info on the net either yet, only had a wee look sofar

[truckarms]

An interesting point on the lpg forum: not sure i agree with him but it is interesting anyway.


Your engine has 5 cooling systems

Your engine has (1) the normal liquid cooling system, (2) Removal of heat by virtue of engine oil to the sump (where the heat is lost to atmosphere by radiation) (3) Direct cooling due to airflow over the engine, (4) loss of heat through exhausted products of combustion and (5) REMOVAL OF HEAT FROM THE CYLINDER HEADS by virtue of the FUEL RAIL to the PETROL TANK.

Your petrol tank is indeed a secondary radiator that you didn't know you had. If you don't beleive that, run 50 miles on gas and then put your hand on the petrol tank. If it is an internally mounted one its temp. will have risen significantly but remember that it has already lost a lot of heat that you will not detect.

If you do not have sufficient petrol in the tank the temperature of the tank will rise more than it is designed to do, the tank will be less efficient at losing that heat because there is less direct contact between it and the petrol due to a reduced 'wetted' surface area. This would not only reduce the efficiency of the overall heat loss arrangements but cause a rise in the temp. of the pump itself which is designed to run cool, not hot.

[dieselboy]

hmm i dont know about that last one, but i can only imagine that being true if the fuel is being pumped to the injectors and then returned to the tank.. however if this is the case, then i bet heat from surrounding areas of the engine bay have radiated to the fuel, and heat from the pump itself would make the fuel seem 'warm' as well. i cant say ive felt my tank to be honest...

since yours is electric then you have it even easier... just fit a switch in the wire. but before you switch back to fuel just make sure you turn the pump back on a couple of seconds before hand. high pressure facet red top racing fuel pumps are only £50.. although they are a little noisey until they are up to pressure. these red tops also switch themselfes off once they are at their pressure. might be a nice idea getting a facet pump.

also, i was under the impression that most standard manufactured pumps switch off at the right pressure???
i remember from other cars if you turn on your ignition you should hear a buzzing noise from the fuel tank for a couple of seconds then it goes off.

[truckarms]

I like the idea of the new fuel pump, and I had thought of sticking a switch in and its still seems the best option. I will have a look at possible pumps.

Mine does seem to always be on, mione has also been quite noisy for a long time now.

As you say the fuel being part of the cooling system does sound like cr4p, I will have to have a look at the tank.

Cheers tonyppe