1500 FWD More Rough Running Problems

[JPB]

.....if there was a fuel blockage/dirt in the petrol etc, why does it ONLY appear UP hills, rather than down? That's the intriguing thing for me.

Perhaps it's simply that the fuel sloshes to the back of the tank on a hill and the pickup is left trying to collect fuel through a pile of flakey bits of paint, tank sealer that's been eaten by modern, benzine-rich fuel or even rust.
Have you tried filling the tank to the brim and then going up a steep incline?

[Jon Tilson]

Its just the basoc laws of physics really...

On our New Gold ots very istructive to look at the rolling MPG readout which goes up to 99mpg on the over run or even more...

On the dead flat at 70 ish it shows about 80 mpg...

the slightest incline brings it down to 45 if speed is maintained.

So what you have is a dicky fuel delivery that can quite happily keep up with the 50 odd mpg you do when on the flat but is hard pressed to give you the high twenties you drop to when going up hill..

I reckon its a tired pump....partially blocked or leaking valves (like the heart condition patient who tries to run but cant though he can manage a walk)

or blocked or perished tubes.

Jonners

[rhisiart]

Thanks for all the interesting explinations and suggestions. Plenty of food for thought there. Much appreciated. I'll give the fuel system a good look over soon to see if I can get to the bottom of the problem. Intersting enough, on the 'full tank of petrol' theme, when I look back on the journey, the tank was full to the brim when I got going, but things only started to go wrong in mid Wales, when the tank was just over half full. There could be something in this ....

[rhisiart]

Forgot to ask ... has anyone I wonder fitted an electrical fuel pump into a FWD or Dolomite instead of the original mechanical one? Would this be possible?

[1300dolly]

Its possible but a complete waste of time and money for an everyday car.

[Purplebargeken]

Any progress?

[rhisiart]

Not yet I'm afraid - due to work commitments, I haven't had time to look at anything in detail. She's still been going ok on the flat, but last night on the way to an important engagement in the pouring rain, I put just a little TOO much faith in the old girl.... yes, she came to a grinding halt on a dangreous bend on a steep hill! The petrol tank was only a quarter full, so the theory regarding the level of petrol in the tank has definitely more credence I think. I've got a NOS tank to fit, so that will be going in as soon as possible, plus another check of the (newish) pump - might also change all the pipe work. The scatter gun approach might bring some positive results, I hope. Will keep you posted. Thanks for asking.

[rhisiart]

An update to the saga .... last weekend, the tank was taken out and it was realised that the tank interior was a real mess, flaky bits, rust, you name it, it was there. Awful. Interestingly - and probably something that added a great deal to the problem - there was a small rubber boot, the kind that fits over a bleed nipple floating around in the petrol! How did that get in? Anyway, my NOS tank was fitted (thanks to a tip-off on this site) and the lines cleaned out with an air-line. One of the petrol filters was full of bits, and was replaced. With the tank a quarter full, I took fate in my hands and took the car up the steepest hill we have locally, the one that I broke down on last week. It FLEW up the hill with no problems - well, it would have done, had there not been a 'new car' driver ahead of me going at a snails pace. Since then, no problems whatsoever. Runs far more smoothly now as well. So top marks to the ones who suggested tank/lines problems. Congratulations and many thanks for all your sterling comments and advice! Appreciated.

PS. The tank sender unit that came with the NOS tank wouldn't work. Brand new, never been on a car, so the unit from my old tank was fitted. Anyone know whether these units are repairable?

[sprint95m]

Excellent news.


Sorry, don't know about the sender unit.

[JPB]

Does the faulty sender have a brass float or a nylon one? I'm thinking that it could have a hole that's allowing it to fill with petrol, which means that it wouldn't then float, so no reading on your gauge.
That would be easy to solve, with a soldering iron. In the case of the nylon float, use the soldering iron to weld the hole closed, in the case of the brass one, then fill [the hole] with solder.
You'd need to place the float in some water and look for the bubbles as any hole in a new unit is unlikely to be visible to the naked eye.

No hole in the float? Then measure the resistance from one end of the winding to the other, if it shows that there's a break in the fine wire then there's your fault.
Lastly, check that the wiper hasn't fallen out of the end of the arm that carries it, this is a tiny (<3mm in diameter usually) carbon pin, they're only held in there by the wire itself.

You can repair the rheostat if the break is within around 2 turns of either end, then it would still read reasonably accurately. The wiper can be substituted by a chunk of carbon from a pencil, HB does the job.

Beyond those things, there's nothing to go wrong with a sender unit, they can always be fixed with patience and a little spot of fiddly work.

[rhisiart]

Wow, thanks! So many experts about everything around this forum. Excellent. Us thickos are very lucky. This one has a nylon float. I'll have a fiddle with it over the weekend to see if I can see where the fault lies.
Thanks

[1300dolly]

glad you have that sorted.

[Jon Tilson]

You can use the wires at the tank and check it looking through the back window. It doesnt earth through the body, only the wires.
Jonners

[rhisiart]

A postscript to the postscript on this matter. I took fate into my hands yesterday and decided to take the old 1500 on a round trip of some 250 miles. It was with trepidation I must say that I set out with a tank full of petrol on a journey that would test it thoroughly, considering the problems I've been having of late. Yes, a mixture of long and twisty roads, small gradients and steep hills, which included going over the Brecon Beacons. It was a great day for a drive, and I needn't have worried at all. The car went beautifully smoothly and surprisingly fast in all conditions, and didn't miss a beat. It was a joy. That's put the ghost of long journeys (and steep hills) to rest once and for all, thanks goodness!

Anyone for a trip to John 'O Groats in the New Year?!

[scoobyh123]

What I should add, for clarity's sake, is that after many stops and starts whilst struggling UP a hill, the car then runs perfectly well DOWN the other side, and then along flat roads - goes like a dream then. It's only when the next hill looms ahead that the funs starts again. Surely - for a non-technical guy like me - if there was a fuel blockage/dirt in the petrol etc, why does it ONLY appear UP hills, rather than down? That's the intriguing thing for me.

If the fuel pick up pipe is at the front of the tank, when you go up hill the fuel will go to the back of the tank. This will be more obvious below a certain level of fuel in the tank, for arguments sake 1/4 tank on a steep enough hill. I quite often get this problem with my Rover if i'm running low on fuel and park somewhere with quite a steep camber or go too quick into a series of sharp bends near where i live. I'm not sure where the pick up is on your car (seem to remember on the 1850 it's at the front of the tank but can't be a***d going to the bathroom to check the Haynes manual!) but how full was your tank when it happened? If it was lowish (say under half full) and the hill was steep enough and the pick up is at the front, it would definitely cause this.

The moral of the tale really is don't go to North Wales!!!

Cheers,
Dave