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Megasquirted V8 Running Issue - Ideas ?


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Ok, just to recap what we know:

It's a fuel pressure problem, but not caused by a faulty component. Correct pressure when running, obviously failing while the engine is warm. It's not the PRV, or a pipe issue.

Must be the fuel pump then, but I'm damned if I can think of a reason why the fuel pump would fail while the engine is warm.

edit: Unless it's something to do with the fuel filter. I would have thought that would classify as a faulty component, but knowing what you're like.... :ph34r:

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Ok, just to recap what we know:

It's a fuel pressure problem, (yes) but not caused by a faulty component (No). Correct pressure when running (yes), obviously failing while the engine is warm (yes). It's not the PRV (No), or a pipe issue (No).

Must be the fuel pump then (No ) ( -2 :rofl: ) , but I'm damned if I can think of a reason why the fuel pump would fail while the engine is warm. (tell me about it, did my head in this over 2 months !! )

-2 and counting

:D

Nige

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Ok, just to recap what we know:

It's a fuel pressure problem, but not caused by a faulty component. Correct pressure when running, obviously failing while the engine is warm. It's not the PRV, or a pipe issue.

Must be the fuel pump then, but I'm damned if I can think of a reason why the fuel pump would fail while the engine is warm.

edit: Unless it's something to do with the fuel filter. I would have thought that would classify as a faulty component, but knowing what you're like.... :ph34r:

-3?

Thinking aloud, isn't there some solenoid gubbins on a standard engine next to the PRV. I can't remember its function because I pulled it off, it's that!

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OK

Here we go V8 Fans

This one was the closest I ever got to being beaten :(

Its a Bowler Racer, and bear in mind this was done over the phone,

I never saw the car, but, infairness to the owner he did EXACTLY

what I asked him to do every step, I didn't get the "I've checked that" etc so

I was sure as we worked through the list that I knew what it wasn't

I was working more towards this being a Mecahical Prob, and not a MS One

More test made me look at the fuel ssytem PRV PUMP FILTER all changed for known

good ones all did Foxtrot Oscar :(

I asked him to check fuel pressure, and he advised one day (Cold Bowler) ignition

on was 35psi :( and then it started and ran fine (Could hear it was sweet)

But, as we chatted he suddenly said "er 33psi now"

:blink:

Whilst I was desperately trying to work oout "Why" he then said "30"

Then "28 psi"

:D

Now, I know a V8 will START at 32+ Psi, and I KNOW a V8 can just about RUN at 28PSI,

BUT a V8 will not start with only 28PSI - and dropping.

So, with temp at 80, pressure was around 26 !

To cut a long story short, I asked him to get a torch and pier inside the fiel tank

REMOVING the pump 1st.

The "Whoop" I heard in the background told me he had found something ......

The Tank was an Aluminum hand made jobbie, my guess is when built whoever tigged it found leaks,

so they shoved some sort of red gloop in there, swilled it about and around and coated the inside.

Its a racer, bounce crash jiggle thump crash bang, the "Coating" had broken up and come off

in bits in places, as the pump was started "Cold" 35 psi from the pump was obtained, but vas

the engine ran (and got hotter) the debris was sucked onto the guaze, being biggish bits

they stuck on the outside, and the pressure dropped as the sh*t stuck to the guaze,

bits are to big to get into the fuel line and hence filter

Switch it off and the debris bit by bit fell to the bottom, and at the TIME it took to get

to 50 degrees, enough had settled back to the base to get enough pressure back to start

He has for the last few nights started ran, switched off resatrted from a clean fuelled

jerry can and all seems lovely, one seriously happy customer :)

Simples :P

Nige

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On a similar vein, the classic motorcycle magazines are alive with stories about the current pump petrol available that has a high alcohol additive (Ethanol?) level which dissolves some fuel tank sealants.

So who actually found the problem?

HfH for getting him to look in the tank or the owner for seeing the problem?

Any way good game and well done for solving it.

Marc.

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  • 1 month later...

Hmmm...... my offroader got jealous of me working (tarting up) my p38 today....lovely heated seats once more :D

So because of this childish jealousy it refuses to start !

It's been running fine the last few days, but today i took it out the unit parked it up... then came to put it back and it was "out of fuel" ... oh *****

So fill it back up with a jerry can and start cranking.

Would start and run for 5 sec's or so then die. Sounds like running out of juice ?

I've plugged in the laptop and reloaded my latest map just incase.

Drained the swirl pot and got a few little grains of dirt out..hmmmm ????

Opened the discharge of the fuel filter and switched on the pump to find fuel coming out.

Taken the return pipe off the return rail (after the standard rv8 pressure reg) and whilst running / cutting out still getting flow.

I didn't have a spare filter to put on it to see if that helped nor did i have a gauge to check my fuel pressure but any guesses ? If the pressure was low, would i still get flow back through the fuel pressure regulator.

Thoughts ?

apart from scrap yard tomorrow !

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Fuel pressure needs to be 26/28 just to get it to run, but more in the region of 35 PSI

Yes, you'll see fuel return at any pressure, but 20 or 30 will look the same !

Will it not keep running if you add revs immeaditely after starting ? (Guessing not)

(If Yes its WUE Maybe out of range in the weather)

If no, then I would

Check fuel pressure

Check PRV Pipework and Tube has vacumn

Nige

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Fuel pressure needs to be 26/28 just to get it to run, but more in the region of 35 PSI

Yes, you'll see fuel return at any pressure, but 20 or 30 will look the same !

Will it not keep running if you add revs immeaditely after starting ? (Guessing not)

(If Yes its WUE Maybe out of range in the weather)

If no, then I would

Check fuel pressure

Check PRV Pipework and Tube has vacumn

Nige

It dies if i rev it.

And it ran eariler this week when it was below 0, it's warmed up since then :o

I'll have a fiddle tomorrow :)

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Haven't touched it again yet.

Also confirm all the gauges in MegaTune are reading sane values, this will tell you if a sensor has gone kaput - start with the basics.

Coolant and air temp looked ok.

Which lambda gauge should i be looking at lambda1 (stays at 1.9 iirc) or lambda2 (stays at 1.0 iirc but needle does fluctuate) although surely it's not running long enough to heat up etc ?

How can i be sure the VR is reading correctly ?

G

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