Andy Moltu Posted April 18, 2017 Report Share Posted April 18, 2017 I don't think the US spec tanks have the returns on the top of the tank - one for the PRV and one for the return from the metering unit. Quote Link to post Share on other sites
barkerwilliams Posted April 18, 2017 Report Share Posted April 18, 2017 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 Quote Link to post Share on other sites
astontr6 Posted April 18, 2017 Report Share Posted April 18, 2017 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. Quote Link to post Share on other sites
peejay4A Posted April 18, 2017 Report Share Posted April 18, 2017 (edited) 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 April 18, 2017 by peejay4A Quote Link to post Share on other sites
John L Posted April 18, 2017 Report Share Posted April 18, 2017 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 Quote Link to post Share on other sites
Kenrow Posted March 21, 2022 Report Share Posted March 21, 2022 (edited) 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 March 21, 2022 by Kenrow added info Quote Link to post Share on other sites
Andy Moltu Posted March 21, 2022 Report Share Posted March 21, 2022 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. Quote Link to post Share on other sites
OldBob Posted March 21, 2022 Report Share Posted March 21, 2022 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 Quote Link to post Share on other sites
Andy Moltu Posted March 21, 2022 Report Share Posted March 21, 2022 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.) Quote Link to post Share on other sites
astontr6 Posted March 22, 2022 Report Share Posted March 22, 2022 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. Quote Link to post Share on other sites
Andy Moltu Posted March 22, 2022 Report Share Posted March 22, 2022 I agree had a PRV stick and was making over 150 PSI! Martins fuel injection - that’s a name from the past. Quote Link to post Share on other sites
saffrontr Posted March 22, 2022 Report Share Posted March 22, 2022 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 Quote Link to post Share on other sites
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