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Fuel Pressure Disappears When Hot...


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Hope you can help...

Took my Manta (A series with GTE injection fitted) out for a spin today in the hot weather.

All went well for the first 10 miles or so, but then she began to miss badly, and then died altogether, and wouldn't even start.

Left her for 15-20 minutes, and she started again and ran OK for a while befire the same thing happened again. (She did this once

last year too, again on a hot day, but I didn't look into it too much at the time. Car has run perfectly in 'normal' temperatures since.)

I fitted up a pressure gauge to the fuel line today, and found that the fuel pressure was disappearing when she started to die.

Am getting around 30psi when she's running OK, but leaving her running in the sun to heat up, fuel pressure drops away and she stops.

I'm presuming the problem is at the pump, or the power supply to the pump. Anyone any idea what might make the pressure disappear

in hot weather? The pump is not especially noisy, and doesn't feel warm to the touch.

Thanks in advance...


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no electrical expert but possibly a resistance issue with the wiring? which could be made worse in higher temps , may be worth getting a multi meter on to the feed to the pump and the earth ? other than that maybe a breather problem , have you tried removing the fuel cap when it starts to run rough?(hot weather leading to a higher than normal pressure build up in the tank)

Edited by pat
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Thanks guys..sorry, should have said that I tried a new fuel pump relay, which didn't help.

I think you're right about a resistance issue..that would seem to fit. I presume if the pump was knackered

it would just be dead, even when she's cold.

I presume I should be seeing 12V at the feed to the pump? Anyone know how much current it should be pulling?

I will see if I can borrow a bench 12V supply from work here and try connecting it straight to the pump...just need

some hot weather to replicate the problem....

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Improvised equivalent to 2p trick.

When car dies "hot wire" a live to the pump (or have in place with switch) and see if it is an instant resurection in which case still relay.

I knew someone with a 1.8 Cav SRi carried a spare, once conked swapped for the one he took off last time it conked and so on for a couple more months.

Also, just because your relay is newly purchsed doesn't mean it wasn't made 22 years ago................

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  • 3 months later...

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