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Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 22242
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a Grand Jeep Cherokee 5.7 HEMI on a 55 plate with an

Resolved Question:

I have a Grand Jeep Cherokee 5.7 HEMI on a 55 plate with an LPG conversion, I had a LPG service last week and was told it's not the LPG causing the problem, when I turn the key in the mornings it rates about 7 to 10 seconds to turn over, not loosing battery power I think it's a fuel problem, when it finally turns over it runs like a dream as normal, please help as I've put it into a Jeep franchise for a service and they haven't got a clue it's quite embarrassing as 17 JEEP stamps in the service book and I feel the after 4 JEEPS in 10 yrs the customer service it getting worse, they want to investigate and I've been told it may take days, surely if it's not electrical it's got to be my fuel pump playing up, can you advise please..regards Wayne
Submitted: 28 days ago.
Category: Car
Expert:  Matt replied 28 days ago.


I'd agree that this sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.
1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

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