Author Topic: Fuel delivery problem  (Read 2645 times)

Ed G

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Re: Fuel delivery problem
« Reply #15 on: May 25, 2023, 03:12:55 AM »
Think,  next week when I'm back, I'm going to run a live from battery to the fuel pump and see if that'll keep the engine running.

Any thoughts on that  good idea or bad?

Lord Voltermore

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Re: Fuel delivery problem
« Reply #16 on: May 25, 2023, 07:23:13 AM »
I'm not an expert but I'd by wary of doing this.  You should already have a live feed which you can check with a multimeter. This should be sufficient for testing whether the fuel pump is working.  If the feed is not live  trace back to source until you find the problem.   

If the problem is because your existing live feed is intermittent it could be due to a safety feature that cuts off the fuel pump in the event of a crash or other situation when you dont want petrol  to continue pumping at full pressure. It may be that the pump is quite correctly shutting itself down due to a blockage or excess pressure build up elsewhere in the fuel supply system.  .     TBH I am not 100%  sure there is such a safety feature, but if there is you want it working properly, not overridden by a permanent  jury rigged live feed.

Even as a temporary feed just  for testing you dont really want fuel to be pumping when is shouldnt . And the pump may stop pumping anyway if there is too much back pressure in the fuel lines  regardless of whether its getting  a live feed. 
If your voltmenter tells you  there is a live feed try  connecting it in a more permanent way  so it can be read from the drivers seat, to see  if the supply is intermittent when driving.   It may help with diagnosis. 

And of course be be wary of connecting electrical connections if you have the pump/filter  unscrewed from the tank due to the risk of sparks. 
« Last Edit: May 25, 2023, 07:30:03 AM by Lord Voltermore »
  I will fix that dripping tap.  No need to keep reminding me every 3 months.

Jocko

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Re: Fuel delivery problem
« Reply #17 on: May 25, 2023, 09:08:13 AM »
Think,  next week when I'm back, I'm going to run a live from battery to the fuel pump and see if that'll keep the engine running.

Any thoughts on that  good idea or bad?
That is what I would do. The fuel pump runs until it reached pressure and then stops, but the electrical feed is still normally present. It is not as if you want the car to drive anywhere. You just want to see if the engine keeps running. Make sure you connect the wire to the fuel pump BEFORE you connect the other end to 12v so you do not get a spark at the pump. And disconnect in the reverse order.
If the engine runs you have an electrical supply fault, if it is still the same, the fault is elsewhere. It could be the pump itself that is faulty. You could remove it and test it on the bench.

Ed G

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Re: Fuel delivery problem
« Reply #18 on: May 25, 2023, 01:01:29 PM »
Update: Right, I plugged the ole manual code reader in and got a P0405 code (don't know why all the mechanics with their scanners all said no error codes), which seems to be something to do with EGR sensor.

So, my plan, from collecting all suggestions so far is: clean the EGR valve, clean the MAF file, Try to start and keep it running for more than 10 seconds. If that fails, try and find which of the 5 wires to the fuel pump is the live feed, and run it direct from the battery to the pump bypassing all the electronics. I'm tied up for a while but should be able to have a go next Wednesday.

Anyone got thoughts on the plan? I'm hoping if all else fails the direct feed to the pump may keep the engine running, though from reading the replies I am not keen on that..  One thing I can't check could be something simple like the fuel pump hasn't got enough pressure to keep fueling after the engine fires, but I guess only way to prove it is to change the fuel pump.

embee

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Re: Fuel delivery problem
« Reply #19 on: May 25, 2023, 01:22:04 PM »
OK, a couple of comments, may or may not be helpful, my suggestions are usually worth exactly what you pay for them  :D

If the alternator has died that could possibly be what's causing the issue. The ECU "expects" the system voltage to drop during cranking but then recover to some degree more or less immediately after the engine starts and the key is released. If it doesn't experience this sort of voltage recovery the afterstart trims/corrections may not be appropriate. This was a typical problem with early generation fuel injected cars when the battery was getting tired and the voltage recovery was slow, you'd often get afterstart stalling.
It may well be nothing to do with your problem.

The other thing is to be sure how the fuel pump is controlled before you try to arrange to power it separately. Often such things are controlled by the ECU switching the line down to earth rather than switching the 12V positive on/off. Putting 12V on the supply side independently might not achieve anything if it still relies on the ECU to switch down to earth. Then again it might be completely different ...................

Ed G

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Re: Fuel delivery problem
« Reply #20 on: May 25, 2023, 01:34:00 PM »
Oh yeah good point, I have a sparea lternator so will be changing that when I do the EGR valve, as that needs to come out anyway, I think, to get the alternator.

Thanks embee

Jocko

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Re: Fuel delivery problem
« Reply #21 on: May 25, 2023, 01:58:21 PM »
According to this wiring diagram, the fuel pump is two wires supplying 12v and earth.

http://www.hondafitjazz.com/manual/A00/HTML/00/SAA2E00000000000000EBAT00i019.HTML

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