Big fueling issues....I give up...Guru help needed. All hands to deck...Pleeeease

V

vipergts

Well-Known Forum User
As many of you know....have done the big engine rebuild with ITB's etc etc

It developed a problem whereby it was holding back (Sometimes) over 4k.

The problem got worse and worse. On a rolling road it was fine

Long story short......Put an inline pressure dial in and could see pressure going from 50 down as low as 25 and could hear the pump struggling.

Work done so far

Another new Bosch fuel pump.....After which the pump/pressure was still playing up
Another new FPR
Another new Fuel filter....this time off a Ferrari thing
Cut tank open and cleaned out and taken restrictive gauze of intake and redirected the return back into the swirlpot

The car has been running well on RR as well as up the road etc pulling really well

So today I picked it up from the shop and within 5 miles started messing up again...fuel pump getting noisy and notably the pressure changing identified by the pitch....Car broke down wouldn't do anymore than tick over

Cooled down and off I went, then playing up holding back again now.

It got me thinking.......could this be a wiring issue?

What is in the line that could give a voltage issue to pump?
 
I think your going to have to give a few more details.

Such as where is the Fuel Pump, how was it wired, existing wiring or complete new loom.

That sort of thing.

Mike
 
On the information given still sounds like a problem with the fuel tank despite the work you've done to it.
 
I have a redtop facet low pressure pump feeding the bosch 044 high pressure pump. Never short of fuel until the fuse blew in the low pressure pump for no reason
 
Fuel pump is where it was from the factory just outside the tank and utilising the original wiring

You have to remember this is a 280 which had Fuel inj std.

I wonder whether the new pump is using more power and if there are relays or other stuff which might impact power to the pump.

Sorry I'm not very electrically minded
 
I'm just wondering if you are having a problem with the fuse box. Possibly a break down in continuity or along those lines. It might be worth just to eliminate the wiring to put a direct feed to the pump and see how it runs.

Now I'm not suggesting hanging a wire out side the car, it would be best to make a decant job of it, a switch and perhaps even a fuse.
 
I think you should look at things that might be different in rolling road vs the real road.
I think engine load, heat, fuel consumption, wiring etc would be similar in both.
One obvious difference would be the motion of the car/tank etc. I.e. on the road you'll have fuel sloshing around in the corners,surging as you accelerate etc.
How much fuel is in the tank? I don't know about your car, but on mine, if I have < 1/4 tank, the fuel surges to the back and leaves the pickup dry.

it does sound like those typical problems with rust blocking the fuel filter etc - perhaps you could remove the filter and flush the line from engine to tank?
 
I should have said that running on the RR very recently with the fuel pressure gauge connected it was fluctuating so there is a problem on there too it would seem
 
Is there any chance that any of the fuel pipes are getting hot in the engine bay or near the exhaust under the car?

If not, the new direct power feed to the pump would be my first look as well as checking the earth to it as well, makes sure there is good clean metal where the earth attaches to the chassis.
 
Just read this quickly so I may be duplicating but have you tried disconnecting the fuel line after the first pump and seeing how good the fuel delivery is and for a sustained period?
 
It sounds like fuel starvation to the pump especially if it's noisy, the bosch pump will flow far more fuel than the original, I would guess the guage of the fuel line could be too small for the pump or a pick up issue from the tank when the car is under load with gravity involved. Certainly doesn't sound electrical.
 
But this doesn't explain why it goes like the clappers other times.

If the gauge of the lines were too narrow then it would be consistently playing up.

I believe there are relays....could be a fault there maybe?
 
My 10p..

Get a low pressure pump to feed fuel into the swirl pot, so that it's constantly full and not reliant on gravity etc.
Common issue when converting a carb car to EFI so worth checking.

Where is the FPR located?

Have you checked fuel return line for blockages etc.
 
Yes I was thinking along those lines

FPR is on the end of the fuel rail. Return line wouldn't affect the pressure dropping so low (I don't think)
 
vipergts said:
But this doesn't explain why it goes like the clappers other times.

If the gauge of the lines were too narrow then it would be consistently playing up.

I believe there are relays....could be a fault there maybe?
Click to expand...

Does it still happen when there is 3/4 tank of fuel?
 
vipergts said:
Rob....there's only one pump as far as I'm aware?
Click to expand...

Ok but my point is to check fuel delivery from as near to the tank as possible and work forwards. The first thing to establish is that fuel flow is not restricted by a blockage somewhere.
 
I've run a Bosch pump for years and the note changes when the fan cuts in or when I run out of fuel. I've recently wired a fuel pressure sensor into the new ecu and the data logs show it steady at 58psi when not on boost. My setup isn't the same as yours though. I have a standard unbaffled fuel tank with the outlet going via a red top to a 2lt swirl pot. Then out of the bottom of the swirl pot to the Bosch 044 via a fuel filter. All this is at the back of the car with the hp pump at the lowest point. The 8mm fuel line then goes straight to the fuel rail with a return line via the fpr back to the top of the swirl pot. The swirl pot also has a short return to the main tank. 044's like a large read line that is as short as possible. As people have already said, you can feed it direct from a red top to ensure constant flow.

I thought you had problems a while ago but only when the tank was half full of fuel?
 
Thanks Johny

The swirl pot on this is in the tank though not with 2 pump system

The return runs straight into it

I thought it was only an issue on half tank but it seems to be at any level. Half the reason we placed the return straight into the pot.
 
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