Fuel starvation, loss of power, engine stops!

[Donners90]

Evening all,

Since re-building the underside of the vehicle over the last few months, I have experienced a few issues with an apparent lack of fuel getting to the engine once it has got hot.

The first time I noticed this was after I had had the engine idling for about 30mins, and the engine spluttered and cut out. I dismissed it at that point seeing as the vehicle had been laid up for a while. Once it was cold again it started and idled fine.

After getting an MOT on the vehicle I have driven it twice, and on both occasions it has spluttered to a stop after about 20mins.

The syptoms I have noticed are:-
1. Engine pops & bangs before stopping (running lean asfuel runs out)
2. Fuel pump does not tick when engine dies
3. Fuel filter gradually empties before engine dies.
4. Pump ticks, filter fills completely and plenty of fuel flow when cold
5. Only happens when engine is hot.

Having searched the forum, there are various topics that seem to cover this type of issue. Some can be found here http://stagownersclub.mywowbb.com/se...uel+starvation

Following suggestions from these topics I have done the following, but to no avail:-

1. Cleaned the contacts in the original fuel pump
2. checked power to pump - 12v to pump and good earth whilst symptoms exist.
3. Dismantled and cleaned inertia switch (wasn't bad to start with)
4. Cracked off fuel pump outlet and fuel spurts everywhere and pump starts ticking
5. Fitted new electronic fuel pump
6. Changed ALL rubber connecting hoses along fuel line in case they were perished
7. Blown air through all fuel lines
8. Fitted new fuel filter
9. Checked fuel pressure regulator & OK
10. Checked the fuel pick-up and it's totally clean, as is the inside of the tank.

I'm now a little puzzled, as the fuel system seems totally clear, in fact the engine runs fine when cold, and pulls V well up to 80mph, until it gets fully hot and you slow down. Suggesting that the issue only occurs when the the engine is hot, and there is less air flow through and under the vehicle.

In one of the posts it suggests that with new silencers (without a heat shield), the fuel pipe can be heated up to the point where the fuel vapourises. I can understand that the fuel can vapourise, but surely the pump would just push fresh fuel through the pipes to the carb. But the pump just stops pumping, as if there is a blockage!

Is it likely to be vapour lock, and would shielding the fuel pipe help? And can a vapour lock stop the pump from pumping?

I would appreciate any thoughts on what to check next, as I am fast running out of ideas!! Or has anyone else had this experience, and/or solved this kind of issue?

Many thanks

James

P.S. Engine is 3.5 RV8 with Holley (recently rebuilt)

[stag74red]

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Hi James, Some of my thoughts:

You say this happens when the car is stationary and moving. If it was heat from the exhaust on the fuel line,I would of thought one of these situations would be different - air flow under car - cooling or heating fuel line.

Does it take approx 30mins after starting engine (stationary or moving)?

What about the carb -

float chamber valves

getting to hot and vapourising fuel

High under bonnet temp (sports manifolds)

high air intake temp - holley pancake air cleaner

If this happens after say 30mins, try cooling the carb with water -does it cure the problem?

Fuel tank vacum build up - try removing fuel filler cap.

hope this may help, Mark.

[comeinhandy]

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The fuel tank vacuum sounds like a good thing to check and the only one that fits the symptoms, especially as you have recently rebuilt the underside. There are breather tubes for the tank that exit under the car at the rear, near the tank. If these got gunked up with underseal that tank vacuum would occur and eventually stop the pump. It also sounds like the carb is working ok as the fuel filter empties, meaning the carb is trying to draw fuel and its valves are open. Good luck!

[Donners90]

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Hi Mark and Comeinhandy

Thanks for your replies and comments.

I intend to check the carb this evening (assuming I can get it to fail again) as I have now checked everything up to the engine. Although I am still puzzled as to why the fuel filter empties, if the carb is not allowing fuel in! I have checked the fuel tank breather system and it is all OK. I even had the petrol cap open when the symptoms last arose.

Also, discussing it with colleagues, I am also going to check the wiring ciruit that powers the pump. If the heat in the engine bay is causing the wiring / electric circuitto heat up this might restrict the flow of current to the pump thus not activating the solenoid coil. I measured 12V at the pump when the symptoms were present, but I could not measurethe current.

If I can re-create the issueam going to give the pump a direct 12V feed from a spare vehicle battery to see if it works. Depending on the results of this, maylead to further electrical investigations! Looking at the wiring schematics, the positive feed comes from thebattery to the ignition switch then via the fuse box before branching off to the inertia switch, and then the pump. As the fuse box is it the engine bay it may be afected by the heat, or if the connections at the rear are corroded in some way they may also be restricting the current flow.

I will report back on my findings

Cheers

James

[Sheepdip]

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I mentioned before about my case but looks like it was a one off in the club. Check the fuel pick up pipe in the tank is not blocked - its tank removal so first try disconnecting the pump at outlet and see if it pumps. In my case the small pick up hole was stuffed with fluff, it ran ok but not at speed.

Paul

[Donners90]

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Hi Paul,

I have checked the in-tank pickup and it is totally clean and clear of fluff. Which in itself is encouraging! Also, when looking in through the sender unit hole, I can see no debris, rust or other foreign bodies in the tank, and the petrol in the tank is fresh.

When the pump was not pumping (due to this issue), I cracked off the outlet from the pump and it sprayed fuel everywhere and started to tick(pump fuel) again! However as soon as I did the banjo back up again, it stopped! I couldn't work out if this was just a coincidence that the pump ticked a few times (I didn't wait too long as I don't want a boot full of fuel!). That's why it is puzzling me, as there is apparently pressure in the lines, the lines appear clear of blockages,but nothing is getting through to the carb when the engine & exhaustgets hot. :?

Anyway, on with the investigations

James

[Sheepdip]

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H James, good thats eliminated that possibility anyway - took me a while to find mine.

"When the pump was not pumping (due to this issue), I cracked off the outlet from the pump and it sprayed fuel everywhere and started to tick (pump fuel) again! However as soon as I did the banjo back up again, it stopped"

Was the engine end connected to the carb still? In which case thats what should happen.

Paul

[RogerP]

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James

I know you say that all the rubber hose has been changed, but did you do the one at the back N/S around the subframe mount? It almost sounds like a piece of the inner pipe is loose and acting like a valve.

Roger

[V Mad]

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The fuel filter is a common reason for concern because it often looks empty. This can happen when any air in the system rises to the filter as it is the highest point, but that doesnt prevent the fuel getting through. You may be on a red herring here as it sounds like fuel is getting though. Just to be sure, wait till it happens again the take of the carb fuel connection, put the hose end in a jar and trun on the ignition to check there is flow.

[Donners90]

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Interesting development!

Right, I think I can safely rule out the pump, fuel lines and electrics! Ran up the engine this evening, with a long piece of clear fuel hose connected between the pressure regulator and the carb. Symptoms returned after about 20-30 mins of running, and the fan cycling a few times. As the engine started to die, there was a fair bit of air / vapour in the clear tube. Engine died, and pump stopped. At this point, I clamped the fuel hose and removed it from carb and put it into a large jar. Undid the clamp and switched on the ignition. Pump fired up and was pumping really well. I clamped the tube again and the pump slowed down and stopped. So I guess that means everything up to the carb is well.

Connected the fuel back up andundid the level plug in the primary fuel bowl and fuel poured out, so the float must be too high.I guess this would account for why the fuel wouldn't get passed the first valve! I duly adjusted this and did the same of the secondary bowl. Whilst adjusting the level the pump clicked away happily when the fuel was flowing, confirming pump OK.

Restarted the engine and it fired well and ran OK, but a little lumpy. Revving the engine it seemed to backfire thencoughed & spluttered. And idled really rough. Not sure what made me check but I thought I'd check the dizzy, and I managed to twist is pretty easily - adjusting the timing!

So the NEW symptoms are, bad timingcausing misfires / late fires coupled with float bowl levels too high stopped the fuel flow. I have suspended investigations until I can get hold of a timing gun to get the engine running right again.

Thanks once again for the comments and suggestions, and I'll update you again (hopefully tomorrow) once Ive got the timing right!

Cheers

James

[V Mad]

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I think you have eliminated any fuel supply problem. Now you need a theory as to what might be wrong with the ignition. If you have points, you should check the dwell angle to make sure the coil is getting the right current. Also check that the ballast rasistor is in circuit by measuring the voltage at the coil + terminal (this should be about 6 volts, not 12 volts).

[Giles]

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could it be the coil breaking down with the heat?

I have had a failing coil in the past that gave pops and bangs as it stopped. Let it cool down and would be ok again for a bit. Also I am not sure what ignition system you have but some of the Rover systems had the amplifier on the side of the dizzy where it gets hot and can also start to fail when it gets hot.

[alan230752]

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Donners90 wrote:

Interesting development!

Right, I think I can safely rule out the pump, fuel lines and electrics! Ran up the engine this evening, with a long piece of clear fuel hose connected between the pressure regulator and the carb. Symptoms returned after about 20-30 mins of running, and the fan cycling a few times. As the engine started to die, there was a fair bit of air / vapour in the clear tube. Engine died, and pump stopped. At this point, I clamped the fuel hose and removed it from carb and put it into a large jar. Undid the clamp and switched on the ignition. Pump fired up and was pumping really well. I clamped the tube again and the pump slowed down and stopped. So I guess that means everything up to the carb is well.

Connected the fuel back up andundid the level plug in the primary fuel bowl and fuel poured out, so the float must be too high.I guess this would account for why the fuel wouldn't get passed the first valve! I duly adjusted this and did the same of the secondary bowl. Whilst adjusting the level the pump clicked away happily when the fuel was flowing, confirming pump OK.

Restarted the engine and it fired well and ran OK, but a little lumpy. Revving the engine it seemed to backfire thencoughed & spluttered. And idled really rough. Not sure what made me check but I thought I'd check the dizzy, and I managed to twist is pretty easily - adjusting the timing!

So the NEW symptoms are, bad timingcausing misfires / late fires coupled with float bowl levels too high stopped the fuel flow. I have suspended investigations until I can get hold of a timing gun to get the engine running right again.

Thanks once again for the comments and suggestions, and I'll update you again (hopefully tomorrow) once Ive got the timing right!

Cheers

James

holleys are sensitive to correct fuel levels,if starvation when hot the holley carb can boil its fuel in float chamber, place a phenolic spacer between carb and manifold

also check for blown power valve,fuel on throttle plates when at rest



alan

[Thurlo Squire]

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Sounds like the coil breaking down under heat to me.

Nigel

[Mike J]

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Sorry to but in so late on this one, but has anyone tried mounting the coil on the bulk head to try and reduce heat build up in the coil. I'm having similar problems so watching this one. Mike