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Bosch Fuel Pump Replacement


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Simon,

 

Running on. There is a thread on the forums "TR4 "RUNNING ON" ISSUE" which was caused by an electric radiator fan. So if other more obvious avenues fail to diagnose your problem this might be one to check.

 

Alan

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Simon,

 

Here are a few pointers

 

Excess carbon in combustion chambers, wrong heat range/type plugs fitted, ignition timing, fuel mixture--A/R & air leak(s) on inlet manifold side. Regarding fuel tank, make sure that the cap seal is vented, i.e. hole in the middle of the seal?

 

Bruce.

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Running on symptoms with PI? Where's the fuel coming from when the pump is switched off? I'd be looking for something keeping the pump running. If it's relay fed from a permanent live supply what might keep the relay energised after switch off? Back end from a fan as suggested above maybe.

Edited by peejay4A
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I'm wanting to improve the reliability of my old Bosch system, and wonder if I could seek some advice please.

I have a bosch 996 pump fitted on the outside, like Gavin has.

The PRV is on the inside of the chassis rail, early TR5,

The CAV filter is still the original and plumbed in, with the bleed pipe out of the top of the filter housing, and the return from the PRV goes into the filter body. I understand that this causes problems and it has on hot days, leave for a few minutes and you can start again.

Should I take out the CAV filter, and install an inline one between the tank and the pump?

Then fit a pressure filter after the pump and before the PRV?

Where will I have to connect the return from the PRV?

Will the one tank return pipe be big enough for the PRV return and the leak back from the MU?

Of the 2 systems I've seen available with pump and filter mounted together from either Malcolm or Moss which is the better?

Any help would be appreciated.

John

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  • 4 years later...

Just to update this a little the Bosch 580 254 979 is now marketed as the Bosch FP 165.

Beware that some do not have the M12x1.5 outlet as shown in the Bosch Catalog.

Edited by Kenrow
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1) Check your fuel pressure. If it is too high the pump will gert hot.

2) Ideally replace the CAV filter a coarse filter between tank and pump to enable adequate, unrestricted feed to the pump but enough to protect from big debris that might damage the pump. Bullitt filter with the coarse mesh cleanable element is good.

3) Fit a fine filter on the high pressure side of the pump to stop small bits of crud reaching the metering unit which is what Bosch did for the Saabs, XR3is and the like.

If the pressure is correct and 2 & 3 in place cavitation should not occur unless the pump is on the way out, the wiring to the pump/earth isn't great, something is clogging the outlet from the tank or the fuel pipe to the pump is collapsing.

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3 hours ago, Andy Moltu said:

If the pressure is correct and 2 & 3 in place cavitation should not occur unless the pump is on the way out, the wiring to the pump/earth isn't great, something is clogging the outlet from the tank or the fuel pipe to the pump is collapsing.

Andy,

could you expand on your comment about poor wiring causing cavitation please.

Thanks

Bob

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It may be a bit simplistic to refer to the problem as pure cavitation when it it may also be vaporisation of fuel in the pump.

If the voltage to the pump is low it runs slower delivering reduced fuel flow so gets hotter as less fuel passing through the pump was to cool itself.  The voltage doesn’t directly cause the cavitation but contributes to heat build up.

The impact of a PRV sticking results in the pump trying to pump against too high a pressure when running slowly and overheating and cavitation occurring.  (At higher speeds/throttle opening more fuel goes to the metering unit and the pressure drops so top end performance diminishes but less likely to cavitate.)

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11 hours ago, Andy Moltu said:

It may be a bit simplistic to refer to the problem as pure cavitation when it it may also be vaporisation of fuel in the pump.

If the voltage to the pump is low it runs slower delivering reduced fuel flow so gets hotter as less fuel passing through the pump was to cool itself.  The voltage doesn’t directly cause the cavitation but contributes to heat build up.

The impact of a PRV sticking results in the pump trying to pump against too high a pressure when running slowly and overheating and cavitation occurring.  (At higher speeds/throttle opening more fuel goes to the metering unit and the pressure drops so top end performance diminishes but less likely to cavitate.)

I have used the same Bosch pump number for over 40 years? The first one was bought from Martin's injection, one of the originators of the use of Bosch pumps and ran for nearly 40 years and was only replaced because of its age. Bosch '0-580-254-952 refers, can pump up to 150 psi. When I replaced the first one they were starting to become difficult to source. One Bosch dealer quoted me 26 weeks delivery. Present situation not known!

Bruce.

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Bruce, I'm still runiing one of Martin's pumps fitted in 1980, still with a CAV filter and mounted in the same place as the old Lucas pump. Never missed a beat in all those years and despite tales to the contrary I can run it until the tank is empty. Famous last words about never missing a beat of course!

Derek  

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