V8 missfire

The main line protrudes up into the tank from the sender unit for a couple of inches and has no gauze cover of any kind, rather it is just the bare metal pipe. The reserve line on the other hand does indeed have a gauze cover, in the shape of a dome which sits right on the base of the sender unit, reaching up barely an inch
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I thought it was the other way round in terms of which pipe is covered ?
 
DaveHerns wrote,..
I thought it was the other way round in terms of which pipe is covered ?
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Hello Dave,

I have a new fuel tank sender unit in front of me, the main line extends up some 95mm and is not covered, while the reserve line is barely there, 5mm at best covered by a very fine gauze dome some 35mm high. On the underside, the main line extends further down than does the reserve,..25mm against 18mm.

Ron.
 
Thank you both, I have a replacement sender but it's 30 miles away in the workshop so I must grab it and have a look. I wounder could the failure of the fuel sender unit be connected to the starvation problem? The previous owner tells me that the gauge started reading erratically and then stopped. His theory is that the unit was damaged by excessive use of fuel additive. Any thoughts? I'm in the process of arranging a transporter for Friday so I can get her out and strip her down for a look.
Regards,
Dave
 
Hello Dave,

I doubt very much that the failure of the sender unit would be in some way connected with the fuel delivery problems. The exit points for fuel and the measurment of the level are quite seperate. The level is determined by a plastic float which is retained by a stiff wire arm. As the fuel level varies, so the float on the arm pivots through an arc, with the position that it occupies converted to a voltage for representation on the gauge.

Either the float could fail resulting in it filling with fuel, so the gauge would always read somewhere less than full depending on the depth to which the float drops, or there could be a failure within the module that relates float position with voltage.

Fuel additives may have contributed to a possible problem with the float, assuming that the gauge problem resides there, but that would not influence a fuel supply problem from the tank.

Ron.
 
Thanks Ron, clutching at straws now! Will hopefully replace the unit on Saturday and at least have a working fuel gauge again. Will probably find out I'm out of petrol!!! :shock:
Regards,
Dave
 
Hello Dave,

Just an idea,....why not take the tank out of the equation and see what happens. Using a few litres of petrol in a drum, rig up one of your electric fuel pumps and feed the hose into the line just before the fuel filter. Run the pump and start the engine. If it runs without misfire, then that would then point to the line between the filter and the tank and of course the tank itself. So far so good.

Now disconnect the line from the tank and connect the test line into the main fuel line at this point. Run the pump, the supply coming from the drum and see if the engine misfires. If not, then the problem is in the tank, if it does misfire then the problem is in the line.

It will be a bit of a fiddle, but it might pay off.

Ron.
 
I doubt this is the same problem you've got, but it serves to remind that inspection is always better than relying solely on the manuals or experience of previous P6s. Prior to your getting the car the former owners might have made non-standard alterations;
My '73 parts donor had a Facet 'push' fuel pump fitted in the engine bay, behind the windscreen washer reservoir in the front, 'sucking' all the way from the tank and higher than the tank outlets. No problems, just an annoyingly loud 'ticking' noise. The engine is an SD1/P6 mish-mash. The oil pump has a pressure sensor that at one time kept switching off the fuel pump after a couple of miles of driving, leaving me standing and most perplexed. Wasn't in my P6 Haynes or Factory manuals because it was an SD1 item. Sender was duff (when I eventually found it and tested it!), new one solved it.
Now that I've written all that I wonder if it is actually in any way relevant. Sorry, late, tired, mind is wandering...
 
Thanks lads. Ron, I'll give that a shot, still haven't got her back to the workshop but hopefully will have a trailer tomorrow or saturday. Will keep you posted. Mrtask, thanks for the tip! Have heard of that one before, some cars use the oil pressure switch to cut the fuel pump in the event of an accident (no oil pressure when the engine stops). However I'm confident that the previous owner didn't mess about with the car (though the owner before him could have!!). Will probably find someone messed about with the outlets or something!
Regards,
Dave
 
Hi all, bounced the back of the car up and down a few times yesterday evening and she fired up and ran perfectly. Think my problem is in the tank. As I've got to replace my sender unit regardless of where the problem is, I think I might remove and clean the tank as there is not much work involved in it.
Regards,
Dave
 
Hi all, latest news on my missfire!! Our regional organiser (and the cars previous owner) has found the problem! He took the car off me for a few days after I helped him sort out his clutch issues, and set about taking the tank out. He called yesterday to let me know he'd found what looked like some heavy nylon tangled on the fuel outlet/sender unit. His theory is that it was used to block the filler neck at some point during the restoration. I haven't had a chance to go see it yet as I'm working long hours at moment, and spent the weekend putting a new flywheel in my modern jag (3 days work :cry: ). Will give more details once I see the car. He is fitting a new sender as part of the job as the old one had failed. This unit had been tested recently by connecting it to the cable at the back and proved to be ok. Now, however, he says the gauge isn't working at all. Aparently grounding the cable at the tank does not move the needle. Any ideas? I haven't had a chance to go see it yet but will try and do some tests at the weekend if allowed by 'er indoors.
Regards,
Dave
 
Does the fuel gauge not take its feed from the Voltage stabaliser? the wire from the tank will be the earth feed or the guague and the 10v required comes from the V.S if this is disconnected or faulty the gauge wont work. I think it also feeds the temp gauge so if it is working the v.s is probably ok.

Colin
 
he'd found what looked like some heavy nylon tangled on the fuel outlet/sender unit.
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Isn't that some sort of filter on the pick up pipe that degrades over time and then blocks the pipe ?
 
Hi all, I thought the gauze only covered the reserve line? The new sender unit i got had a small filter over the reserve outlet. This, aparently is quite big. I haven't seen it yet due to work and my broken every day car. Will hopefully get to the ROs place on saturday to see it first hand. Need to have a look at the electrical problem myself as well if I get a chance.
Regards,
Dave
 
Hi

I was told the nylon filter covered the main supply .I've never had it out to look . Blowing down the pipe with compressed air certainly shifted whatever it was that was blocking my main supply
 
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