Fuel Pump Overheateded?

[Guest pwlcarz]

I took my S7 down to the Goodwood Revival on Saturday.

 

The car ran fine on the trip down from Gloucestershire but about 2 miles from Chichester we ran into very slow moving traffic - the queue to get in to Goodwood.

 

After about 20 minuts in the stop/start traffice the engine start running a bit 'lumpy' then just cut out and wouldn't restart.

 

After pushing the car to the side I took off the bonnet and checked the fuel flow into the carb - nothing. I then took the pipe off the inlet to the mechanical pump and there was petrol coming out, so guessed the fuel pump had failed, a call was made to the breakdown services.

 

While waiting I had a few thoughts about the mechanical pump and couldn't see what could have failed as it operates from the Dizzy drive. A sudden horror thought the the Dizzy/Oil pump hex drive shaft had failed again (older readers may recall the issues I had with this a few years ago). but a quick check taking the Dizzy off appeared to reassurure me the shaft was still in one piece!.

 

When the recovery guy turned up I explained what had happened and he went through the checks on the fuel lines again - no fuel coming out of the pump when you turned the engine over but fuel freely going in to the pump.

He then sucked fuel through the pump and when we turned the engine over again there was fuel coming through fine. Reconnected the pipes and re-timed the engine (roughly) where I'd taken the Dizzy off and the engine was running fine again.

 

The recovery guys suggested that sometimes the operating lever in the pump expands if the engine gets very hot and starts sticking thereby causing fuel starvation.

 

Anyone heard of this before?

 

Any likely cures (short of moving over to an electric pump)?

 

Cheers

[Grim]

i assume you have the little plastic insulator fitted between pump and block?

[Guest pwlcarz]

Yup! That's there.

 

Wonder if it would be worth changinmg over to an electric fuel pump.

 

anyone know what's involve?

[miikae]

1 electric pump , say Facet and fuel pipe

2 relay

3 inertia cut out switch or some such to be safe

4 switch for turning pump on/off manualy

5 cable to wire it all up

6 possibly a pressure regulator/fuel filter to bring the pressure down to approx 2.5 psi for carbs

7 ignition 12v supply

8 seperate fuses for both pump power circuits

9 the will to do it

10 finding the time

 

And bob's your uncle Brum Brum and away yee go

 

Mike

[johnlrichardson]

Stick with the mechanical pump It will last longer Worked on many Pintos over the years and never had trouble with the pump sticking may have been muck under the valve seat

 

jon

[IanS]

New mechanical pump is cheapest option.

Only held on by 2 bolts and the fuel pipe.

[ibrooks]

I'd be more inclined to suggest that the problem was fuel vapourisation than a problem with the pump itself. I certainly get it on the GTM if I end up sat in a queue. Underbonnet temps rise until the fuel in the lines vapourises and the pump then has gas rather than liquid in it. The only option is to let it all cool down for about ten minutes and then re-prime the pump (liquid pumps aren't generally good at self priming) and off you go again.

 

One option I've looked at is a leccy fuel pump from a carbed car near the tank to use as a primary lift pump. Should prevent it happening by keeping a little positive pressure in the line behind the mechanical pump.

 

I haven't thought about it to the nth degree as I'm planning to fit a twin-cam head and run throttle bodies which will elminiate the problem by having a high pressure pump outside the engine bay.

 

Iain

[Andy Spencer]

Hi Peter

I suffered twice going to Le Mans in queues with that car with fuel vapourisation when it got very hot (30 degs + and very long queue!) but never in this country. Would always re-start after a couple of mins though, and of course it was the older 1.6 engine.

 

I'd still say fuel vapourisation. Did I hear you say once that you had reduced the 15 odd mm gap between the bonnet and chassis sides? If so you could be restricting cooling air flow around engine and making the problem worse, as that bonnet had no vents in (at least when I had it!). Keeping good airflow around the engine will help, and your new electric fan should add to that help. But if the air can't get out from underbonnet then temps will rise to fuel vapourisation point.

 

I'd ensure good airflow and keep the mechanical pump, which was new with the engine refurb so won't have done many miles. Only about £20 new if I remember correctly though for peace of mind.

[Guest pwlcarz]

Hi Andy.

 

Still got the gap along the bonnet sides, and I added 1 vent above the exhaust.

 

Think you may be right about fuel evaporation - it was very hot and I could barely touch the bonnet and scuttle cowling.

Interestingly the water temp was OK - didn't actually boil up!

 

I'm just surprised it got so hot so quickly. Mind, I'd been running on the M27 at a good 70mph, then almost immediately got off and got stuck in slow moving traffic.

 

I shall have to do some more investigation and see if I can get more cool air to the fuel lines - maybe duct air in from outside perhaps!

 

Something to look at over the winter!