Author Topic: Hot starting issues following fuel pump replacement  (Read 111 times)

adamb

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  • 1977 450SEL6.9
  • Location: London, UK
Hot starting issues following fuel pump replacement
« on: 09 May 2020, 01:07 PM »
Recently I replaced the fuel pump, filter and the surrounding hoses. Since then my car had developed a hot starting issue. Clearly pressure drops and fuel vapourises. I need to floor the throttle and crank and crank for it to start. Very unglamorous as the car draws so much attention anyway. I wonder why that may be the case. Does the fuel accumulator by the pump play a role in maintaining pressure after the pump is switched off? Or course, this could be coincidental but it seems too much of a coincidence. There are no external leaks.


ptashek

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Re: Hot starting issues following fuel pump replacement
« Reply #1 on: 09 May 2020, 02:33 PM »
Yes, it does play a major role.
It keeps residual pressure in the system once the pump is off, preventing vapour lock.
Starting the car hot with one of these failed is a massive pain in the proverbial, and the symptoms you have described match perfectly.

Easy to test. Start the car as normal, switch off.
Remove the return pipe on the accumulator. If fuel comes out, that's a clear sign the diaphragm is ruptured and you need a replacement.
1993 "Pearl Blue" W124 280TE
1979 "Icon Gold" W116 450SE (history, resto)

Randys01

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Re: Hot starting issues following fuel pump replacement
« Reply #2 on: 10 May 2020, 05:04 AM »
yes.    surely accumulator??