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Fuel gauge faulty, ran out of fuel, now engine won't start.


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Hi fellow 'Early models' (1974) - I know these gauges are notoriously unreliable, but mine has now become an un-trustable paperweight.  Upon removing, I can see a spade connection is like a child's wobbly tooth. Anyone know where I can end it for restoration, or perhaps know the whereabouts of a replacement item?

The gauge read 1/2 full when I ran out of petrol at the weekend. I filled up at Morrisons and now my car won't start at all. It tries to start, but only for a seconds.

Blockage or coincidence perhaps? Or does a fault gauge also screw up the ignition system somewhere? 

Thanks, Marcus

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13 hours ago, Ian Comerford said:

The gauge may not be faulty, it could be the sender in the tank.  It is possible to remove, strip and clean the sender to make it more reliable

I had this one time. Got all the way to the Alps with a still full tank. Took the sender out and gave it a gentle shake, put it back in and the gauge dropped to zero :o

Fortunately it was all downhill to the petrol station. The sender wires are fragile, so be gentle.

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18 hours ago, Lesworth said:

Likely crud pulled in to the fuel system. Does it have an in tank fuel filter? Are you getting fuel to the injectors when cranking? If not then either in tank or main fuel filter may be blocked.

I replaced the tank with a Dansk one during the 2015 total restoration and full engine rebuild. The tank sender unit was replaced with a genuine Porsche unit.  Also replaced the air box when it blew apart in 2018 and had all the pressures and vacuum levels set at Autofarm. Was warned that the WUR was well past it’s best and recommended a recon soon.  Not drive the car much over the last 2 years (been in storage).  Have just sent the WUR to KMI for a rebuild. Everything else in the fuel system is new (Pump, Filter, Accumulator, Connectors) so it’ll be a start point.  

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17 hours ago, Leicestershire said:

If you have run dry on fuel, the system may need bleeding.

With the ignition switched on, lift the airflow sensor in the airbox to force the pump and prime the lines. 

7 or 8 seconds should be enough. 

i tried that first. Have bitter experience of a blown air box in 2018.  The fuel pump is often noisy (it was replaced in 2019).  I believe it’s the check-valve vibration because 1974 models don’t use a DME relay, the pump is on all the time the ignition is on.

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  • 2 weeks later...
On 14/10/2022 at 15:08, Lesworth said:

Likely crud pulled in to the fuel system. Does it have an in tank fuel filter? Are you getting fuel to the injectors when cranking? If not then either in tank or main fuel filter may be blocked.

After a process pf elimination starting with the injectors (I tested 2 -had  same problem of weak erratic spitting).  I then checked the fuel flow from pump (at the accumulator input) - should be 750ml in 30 secs (1000 on later pumps) - this was a measly 100ml.

I then checked all the electrics to the pump, which was noisy with inconsistent metallic spitting - I had 12.5v (spec is to have min of 11.5V).

I checked the airbox for leaks by blowing cigar smoke into the injector socket. No leaks. This is good because I replaced this in 2018 and it wasn't cheap.

Next was to try to bleed at the pump. I connected a clear hose to the accumulater input and this showed a measly flow, with lots of airlocks, which coinsided with the metallic spitting pump noises.

I removed the fuel-level sender - the tank looked clean inside. It's a Dansk tank I bought new in 2018.

I then tried a tip from a member on the Pelican forum - blow air back into the tank via the return pipe - the bubbles may dislodge any crud in the anti-swirl area at the bottom of the tank.

I connected a bicycle foot pump to the metal return pipe at the engine end. Set up my iPhone on the tank to record 'sounds' inside the tank, and gave a good few hard pumps.  The iPhone recorded at big whoosh of bubbles and rush of fuel.

I checked the fuel flow at the output of the pump (accumulator end) and yahoo!! a solid, high flow of fuel. I checked the flow rate and it was over 1000 ml in 30 secs.  It is a new Porsche pump bought in 2019, so I was hopeful it had not failed.

Bled out a further 5l of fuel (via the fuel pump) to check flow rate stayed even and consistent. The long clear pipe I was using showed there was no air in the flow and all the pump's inconsistent metallic spitting noises had gone. Connected up all the lines and tested at the injector again - lots of lovely mist - perfect. Feeling hopeful.

Checked all connections again and then turned the key - started first time up and runs evenly.  Ran it to hot to clear out all the WD40 and carb cleaner I had used everywhere.

Next job is to get the tank flushed out in case the crud is still there and has just moved about.

During this saga, I sent my WUR off to KMI to get it rebuilt. Came back looking like new. It is a 1974, first gen model. Steve (at KMI) said it was rotten inside and no way would have been working correctly.  He sets them slightly richer than spec to avoid the low revs jerking which he says is a characteristic of early model WURs. Will test drive tomorrow to see if it has fixed it.


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On 29/10/2022 at 09:08, Ian Comerford said:

Good luck with the test drive.  Steve at KMI has done my WUR and recently the fuel distributor, the car ran much better after each was refitted.  He does good work

Reporting back - the car runs really well. No jerkiness around the 1500 - 2000 rpm range. Can pull away smoothly in 2nd and 3rd gear, and driving just-oof the throttle is no longer a kangarooing issue. Refurbished WUR has fixed all the problems - wish I'd done it years ago.

The starting problem, though was airlock in the fuel feed to the pump. Either an airlock, or grid in the tank. Fixed by blowing clean air back down the fuel return pipe into the tank.







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