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+--- Thread: Fuel pump on it's way out? (/showthread.php?tid=1726)
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Re: Fuel pump on it's way out? - Rissy - 31 Jul 2012
...Just as an add to this thread, and for some addtional information, I had this noisy vibrating fuel pump issue on Wednesday last week for the first time - I didn't know what was causing it. It was quite alarming at the time.
I was a little worried about this, but the next day the problem seemed to have gone again. Only after talking to Stunned_Monkey and Rich_H on the following Sunday did I learn about what this was.
So for prosperity, here's a scenario to explain, in case anyone gets something similar in the future...
Wednesday was a really hot day, really HOT. After about 2.5hrs of driving, towards the last 40mins of the journey, traffic slowed, and this resulted in eeking the last few miles at slow pace.
With the heat from the cooling water system surrounding the fuel tank and acting as a radiator, and then finally the cooling fans kicking in, resulting in hot air being blown on to the fuel tank too, the fuel temperature got VERY hot!
This in turn, softens the rubber hosing coming off the bottom of the fuel pump (The funny "?" shaped hose). With the suction of the hot fuel through the softened uptake hose, the walls of the hose collapse inwards, essentially trying to block the supply of fuel to the pump.
The pump then struggles to continue to pull fuel up out of the tank, causing it to work harder and louder.
This increased noise is then emphisised as it's sitting inside the tank, which acts like a drum, and amplifies the noise, making it sound awful, and quite disturbing if you don't know what it is. You can actually feel this vibration through the gear stick! (on a manual car at least)
It's the same vibration you feel when you turn the key on the ignition to stage 2, which results in the fuel pump priming itself briefly to prepare for the engine requiring fuel at the follow up turn of the key to position 3)
This increased stress on the pump, exhibited by the noise, over time and exposure, will shorten the lifespan of the pump. It will eventually burn it out (increased stress, means more heat from the motor, meaning hardware eventually breaks down).
There are 3 solutions:
1. As stated above, the "CoilZilla" (Unofficial name) approach mentioned by RichH which involves threading a coil of stiffish wire down the pipe (removing it from the tank first of course) to stop the pipe collapsing. (Make sure that the coil of wire doesn't pretrude past the end of the pipe which connects on to the pump - obvious, but worth mentioning. Also, don't leave the coil of wire in such a way that it may puncture the hose, especially when it softens, or of course, during application of it inside when its detached from the car)
2. Put nice new cool fuel in the tank at a service station
3. Stop the engine and go away and have a cup of tea to give it time to let the fuel cool down inside the tank again (meaning the hose pops out to normal shape again)
It's quite a rare circumstance to get this noise - it requires quite extreme conditions (or a particularly old fuel hose inside the tank to make it happen more often - at this point, replace the hose to make sure it doesn't split, meaning it could start drawing in fuel further up than expected, meaning it could start drawing air rather than fuel, if the level in the tank drops below where a split may be)
Other than this, it shouldn't happen to many people that often.
Re: Fuel pump on it's way out? - Chris Williams - 31 Jul 2012
As I understand it this is a common problem in the US (more so in the hotter states) and seldom occurs in the UK due to lack of hot days!!!
Specialt auto does a 'hot air dam' thats supposed to help but how much who knows http://www.specialtauto.com/delorean-pa ... -fans.html half way down page
Chris
Re: Fuel pump on it's way out? - stunned_monkey - 02 Aug 2012
If you have a reproduction pickup hose, it shouldn't be collapsing but the hot fuel and the restriction caused by the pickup filter is enough to cause cavitation within the pump.
I think the "hot air dam" is completely missing the point that the fuel tank sits atop the hot coolant pipes. When stuck in traffic, these get hotter (ie running up to fan temp) and you lose the cold air flow of the car moving forwards. The hot air dam also ignores the massive steel box which is between the tank and radiator anyway.
Re: Fuel pump on it's way out? - Rissy - 02 Aug 2012
Exactly. This was my thoughts. Also, since changing my Otterstat earlier in the year (due to leaky rubber grommet of original - anyone know how to just get the grommet rather than replacing the whole switch!?) my fans come on later (Changed the switch for a new Volvo one - i think its an 85-96?) so on the occasion above, my fans hadn't even come on yet, meaning no hot air being blown backwards, only ambient temperature being boosted by the cosy radiator effect from the water cooling system. Still enough to get the pump to start complaining - cavitation or collapsed pipe?...
Re: Fuel pump on it's way out? - Guinney1971 - 02 Aug 2012
I may well have some pictures of 'springzilla' somewhere on my computer, I'll see if I can
find them and post them up to go with your write up Rissy.
Again, this could be a good one to go in a future Club Mag as a techy how-to
Re: Fuel pump on it's way out? - stunned_monkey - 02 Aug 2012
It used to be worth doing when the replacement pickup hoses weren't available except ludicrously expensive and had exactly the same problem, but they've long since been available in a non-collapsing guise for $42.
Re: Fuel pump on it's way out? - Rich H - 03 Aug 2012
Quote:but they've long since been available in a non-collapsing guise for $42.
Well hopefully better than my 'new' one which I bought when I got my D
That did a great job of collapsing on the way to Harpenden Classics on the Common
(the year I got stuck on the motorway and you all waited for me outside a local pub)
Fortunately it's not been that hot since, so I've not had the problem again...
Re: Fuel pump on it's way out? - Guinney1971 - 03 Aug 2012
so its YOUR bloody fault the weather's been so cack! :lol: