Fuel Pressure too high

Unusual to have a high reading not a low one I know, but I changed my D2 fuel pump for an Allmakes own one (given to us as a demo) and I am getting a fuel pressure reading of 9 bar. When the ignition is switched on it briefly hovers on 4 bar then climbs to 9 bar and then constantly flicks between 7 bar and 9 bar. Stupidly I did not take a reading off the old pump as I only changed it due to whining constantly, although it did seem to run ok.

Question is whether this is definitely a problem with the FPR or not regardless of the condition of the pump?

fpr is what regulates pressure unless return is partially blocked

jamesmartin said:

fpr is what regulates pressure unless return is partially blocked

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That;s what I thought so I popped off the return pipe on the filter housing and diesel flows out.

fpr is first choice then,pump only produces pressure due to fpr

I am wondering if someone has plumbed up the fuel cooler wrong... when I changed the pump the fuel hose on the cooler started popping off. Fixed that and then it blew the high pressure hose that runs along the inlet manifold. Looking at the fuel system diagram diesel is meant to go in the cooler on the off side outlet and back to the filter head via the one nearest the engine. When this hose was popping off diesel was coming out the cooler not the hose. Not sure if it matters, whether the cooler is just in and out or if it's one way

Scrap that idea it’s plumbed the same on my other d2

Where did you connect the gauge? ...are you sure it's working well not overreading?

normal HP direct outlet from pump should be around 6 bar(+/- 0.5)

sierrafery said:

Where did you connect the gauge? ...are you sure it's working well not overreading?

normal HP direct outlet from pump should be around 6 bar(+/- 0.5)

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The gauge is connected in the fuel temp sensor outlet. I normally see 4.5 - 5 bar on most vehicles with the gauge hooked up in this location.

Also, the pump is "working" in line with the pressure readings. It sounds as though its switching on and off although there are no voltage fluctuations.

tom1979 said:

The gauge is connected in the fuel temp sensor outlet. I normally see 4.5 - 5 bar on most vehicles with the gauge hooked up in this location.

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IMO your gauge is overreading anyway then cos in that port it's supposed to be 4 bar regulated pressure(provided the FPR works well) but even so you should not see 9 nor 7 bar there whatsoever

tom1979 said:

I am wondering if someone has plumbed up the fuel cooler wrong... when I changed the pump the fuel hose on the cooler started popping off. Fixed that and then it blew the high pressure hose that runs along the inlet manifold. Looking at the fuel system diagram diesel is meant to go in the cooler on the off side outlet and back to the filter head via the one nearest the engine. When this hose was popping off diesel was coming out the cooler not the hose.

View attachment 198568

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fuel goes through fpr round head back to fpr then round cooler from bottom hose in fpr, top been the feed from pump to tank

Any help?

raywin said:

Any help?

View attachment 198571

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I think I have memorised that diagram since yesterday

I went back out at 4pm, put the ignition on and it’s running perfect now, holding 4 bar and no more or less. I’m stumped what caused it, I hadn’t changed a thing in between.