The Triumph Dolomite Club - Discussion Forum

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PostPosted:Mon Jul 19, 2021 8:56 am 
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I've been scouring the forum for similar issues. Yesterday at the HERO Regularity rally in Chesterfield my trusty Sprint coughed and spluttered then died going up a hill. Having done my limited best to determine the fault, the backup maintenance crew arrived on scene. They quickly ruled out electrical and focussed on fuel supply. Like magic in 15 mins they bypassed my mechanical fuel pump and fitted a temporary electric pump (& new filter) under the bonnet. After some priming difficulty, up it fired and we were good to go. We tore off to the next Stage only to encounter a significant hill again. All was fine (even great really) until near the top again when the same problem recurred. Given the time of day, we bailed and headed back to the trailer...which was easier to write than do. Every hill we came to we either had to back down and find another route, or slowly limp up - spluttering all the way. So... On level ground I can give the car full beans with no issue at all. As the road inclines uphill I get the odd cough which, the steeper the incline, can be terminal. It is totally incline related. This is the part that I can't really understand. If, I was pulling air into the fuel line what would a hill have to do with it? Could I be pulling air into the tank outlet (within the tank itself), this might make sense with a half full tank? Could there be a bit of crud which only blocks the outlet on an incline? Theoretically this could have been disturbed on one of the fast gravel tests - I did bottom out pretty heavily a couple of times! I'm a bit dubious about this because it's not random at all. Just incline related.

I note that the electric pump in the bonnet has the same suction distance as the mechanical pump. So maybe change out the whole fuel line. I guess emptying the tank for a good look see makes sense too.

The incline bit has me baffled though....and the fact that it seemed to get progressively worse. By which I mean that it had happened earlier in the day. I switched spark plugs and all seemed good (though obviously it was just the rest it wanted :roll: ). We managed another 2 regularities and 4 gravel tests at full beans, without issue. Then the second regularity after lunch the problem I described above re-appeared and then just got worse.

Perhaps all the banging and shaking on the gravel tests? Err.... Ummm.. :( ?

And advice would be most welcome
Thank you


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PostPosted:Mon Jul 19, 2021 12:19 pm 
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Hello.

I remember a couple of issues that Richard Old suffered with on his fleet over the years which are similar to yours.

One issue was a very slight pin hole in the fuel line, just as it goes over the rear axle - this had rusted through and was giving problems drawing in air. I think this too was on an incline and I presume due to the increase in 'suck' required uphill without the aid of gravity - this was when the air was sucked into the system.

The other issue he has had was with the petrol cap - this is covered in this thread:
https://forum.triumphdolomite.co.uk/vie ... hp?t=14646

Hope that helps!
Best wishes

Matt.

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PostPosted:Mon Jul 19, 2021 1:34 pm 
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When I got my 1850 it did this,
replaced the inlet manifold gasket to effect a cure


Ian

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PostPosted:Tue Jul 20, 2021 11:20 am 
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Had a car and that did this in the past, turned out to be a small amount of water in the fuel tank.


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PostPosted:Wed Jul 21, 2021 4:29 pm 
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I have only just read Matts comments about the problem that I had. As the fuel line over the rear axle is above the the level of the petrol tank if you get a hole in this area fuel will not leak out but the fuel pump will draw air in through the hole and at some point it will not drawer enough petrol to keep the cars engine running.


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PostPosted:Thu Jul 22, 2021 9:56 am 
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Thanks everyone for your replies. I suffered an horrendous dose of food poisoning following the rally :( so I've been lying low

Pinhole leak makes sense (water too I imagine as the tank was half empty at this point). I didn't mention that it was seriously hot on Sunday and so I am learning that vapour locking could have been the/ an issue. I have bought an electric pump which I will mount adjacent to the tank. I guess any leaks will be pretty damn obvious then and by placing it next to the tank I should overcome those vapour locking issues too. That's a job for the upcoming weekend now I can venture more than a few steps from the little boy's room. I just need to get a fuel inertia switch for comfort and then we'll see if it happens again!

Thanks again


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PostPosted:Thu Jul 22, 2021 3:31 pm 
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Not all electric pumps are suitable for in the engine bay so moving to the rear is a wise move. You can fit a fuel pump relay and a Ford one does fit in a normal 5 pin socket. When the engine stalls the pump goes out. When switching the ignition on the pump primes for a few seconds and stops. When crancking the engine the pump starts running again.

I do fit inertia switches also but then with a relay the other way around and not the pump but ignition coil. Switch off, relay on to stop the coil feed, what does stop the fuel pump automatically because of no spark anymore. Sometimes at regularities driving through a pothole does activate the switch and makes the car stop. Connecting it the other way around you can pull the connector from the switch on bumpy roads. Having such a fuel pump relay and inertia switch is the safest combi.

My guess is water in the tank.

Jeroen

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