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6 cyl Bristol cars Type 400 to 406 - restoration, repair, maintenance etc

Fuel starvation (403)

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Old 27-03-11, 08:05 PM
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Default Fuel starvation (403)

Driving home yesterday I got to Reigate Hill and as I started up the engine gave out. Sometimes it would start but wouldn't pull away.

Eventually I got it running and turned around as I didn't want to risk stopping on one of the more dangerous parts. I took a flatter route home with one further problems.

Any suggestions as to the cause? Might it be causing the miss fires on the run?

Peter
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Old 27-03-11, 08:48 PM
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Easy old man! Gas or electrics....you can eliminate other issues such as tire pressures. LOL
Weak pump....fuel blockage. Bad coil acting up intermittently and when hot.
Get a spare coil of the same ohms and see if you are happier. Blow back through the fuel line so as to clear it, and or crank the engine over with the fuel line loose at the carbs and see if lots of fuel come out.
Old cars area lot of fun...keps us laughing all day!
Cheers,
Dorien
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Old 27-03-11, 08:58 PM
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Default Fuel Starvation (403)

Peter,
I had a similar problem some years ago with my 400 when fitted with 3 Solex carbs. Along a flat country road it performed very well until I encountered a relatively steep hill , it then ran out of power and I had to pull over. There was plenty of fuel on the tank , the pump was working well but when I checked for fuel in each carb I found that one was almost empty. The best way to check that is by removing the brass main jet holder on the drivers side of the carby.
The brass float was jamming in the carby body and not allowing enough fuel through when it was needed climbing a long steep hill.
I removed the carby top and with some fine sandpaper smoothed the three float guides on the inside walls of the float chamber . I then had no further problems .
I'm not suggesting this is your problem but it would be worthwhile checking each carb for fuel when you encounter the problem again.
Good luck

Geoff
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Old 27-03-11, 11:48 PM
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Default Fuel starvation

I would check the diaphragm in the fuel pump. If this is damaged, or possibly not correctly centered, then under acceleration it masy cease to function, and it can be quite intermittent.

Sean
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Old 28-03-11, 02:51 AM
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Happened to me recently going up the nearby Titsey Hill, Limpsfield.
It was the coil beginning to give up. Fine when not under load,
ie on the flat or downhill, A new coil rendered normality.
Let us know how you get on.
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Old 28-03-11, 10:06 AM
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Default Fuel or electrics?

Could well be fuel starvation as others have suggesrted (I've had that happen too) but don't forget the condenser - a weak condenser can give exactly similar effects, the engine will start (sometimes) but the condenser breaks down when the engine is under load, shorting out the LT electrics. It's an easy one to check out, just in case.....

Good luck - these things can be very frustrating to get to the bottom of....!
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Old 28-03-11, 10:45 AM
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Peter, Check your distributor points to make sure they have not closed up, this is likely to be the most likely fault.

My regards,
Bellerophon
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Old 29-03-11, 11:52 AM
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To clarify a little, I was at the bottom of the hill (not very steep) in traffic traveling, slowly at low revs.

Had the car tuned yesterday. Southern Carbs said there was little wrong. There was a slight ovality of the (butterfly?) spindles which allowed a little air past at low revs which causes a little hunting. 3 & 4 pots are burning oil which they thought was causing the mis fires and the clutch is dragging.

A new MG B clutch has been fitted. It doesn't bite until the end of travel which I am not very keen on, but I am told that is the way of modern clutches. When disengaged engine revs drop by some 300 revs.

The engine was reassembled with new rings and the clutch fitted coming on for a 1,000 miles ago. It has been carefully run in with occasional squirts upto 3,000 and then 4,000 revs latterly.

Regards, Peter

Last edited by peterg; 29-03-11 at 11:53 AM. Reason: mistype
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Old 29-03-11, 03:28 PM
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Start with replacing the cheap bits that can cause this sort of problem. Condenser, fuel filter, points and electrical connections and move onto the other suggestions until all is well.

Normally the last thing you try that fixes it :-)
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Old 31-03-11, 04:19 AM
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I would first check the spark plugs, to see how the engine runs. Too rich fuel/air mixture?
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Old 03-07-11, 11:02 PM
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Things have gone from bad to worse.

Going to the Bristol evening at the Ace Cafe it gave out in heavy traffic at West Ealing. Again going slowly up hill. Eventually got it going after lots of cranking, manual priming of the fuel pump and lots of false starts. No problems on the way home.

The following Tuesday, just south of Dorking, going up a dual carriageway hill at 60 mph I put my foot down to get past a RAV4 and the engine faltered. Eased back and managed to hold 50 mph but again heavy traffic outside Horsham saw it give up. Once more priming and cranking got it going for a couple of hundred yards, twice, before finally giving up the ghost.

Now to the questions:

How full should the pump bowl be? It fills on priming with lots of bubbles but the level drops back down to the gauze.

It was suggested that the pipes in the fuel tank were perforated but they seem fine. Can the reserve pipe solenoid be overhauled? Should it? I am told that it will pick up the sludge from the bottom of the tank.

Can anyone recommend a good coil & condenser? I left the ignition on while trickle charging for 5 days. It was rather hot when I checked it this evening and I am guessing it may have burnt out.

Woe, woe and thrice woe.....
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Old 04-07-11, 09:29 PM
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Apologies is this is a horribly basic and obvious comment, but I don't think there should be bubbles in the fuel pump. I got that on mine when the seal around the glass dome started leaking, so the pump was partly sucking from the surrounding atmosphere, not the fuel line. Holes in the diaphragm would give the same effect.
Hugh Miller
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Old 05-07-11, 09:22 PM
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Apologies not needed. I just want to solve the problem. Could the 'petrol' be eating the seal? It has done the most appalling things to the tank sealer on my motorcycle, causing no end of bad running and blockages in the carb.

Roll on 10% ethanol!
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Old 03-08-11, 05:00 PM
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Default 401 too

Have just bought a 401 at auction. Misfire & acts like fuel starvation. Replaced distributor, rotor, condenser, spark plugs ... no change. Replaced leads & caps and was great for a few miles but now at over about 45mph feels like fuel starvation too.

My pump has dirty looking fuel (my Redex?) well up the glass bowl.

I had not thought of changing the coil nor of looking in the carbs ... fuel squirts down the barrels very nicely on my driveway anyway. I have the patience for all this, but do I have the time? Aaaaaargh.

Last edited by Michael English; 03-08-11 at 05:01 PM. Reason: typos
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Old 09-08-11, 06:43 PM
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I think that I have found the cause of my problem. The solder on the ferrule of the inlet to the fuel pump had failed. Just resoldered it and will refit next week.

Found it when I took off the fuel pump and cleaned it out. An easy job to do. Got a repair kit from Teesdale Garage in Nottingham.

Next job is to reassemble the reserve solenoid unit. I don't think it is worth the 200 to overhaul it. I want to lengthen the short pick up pipe to match the reserve but the plumbers merchant says brass is difficult to solder to copper. Does any one have experience of this? Are there alternative ways?

Is there an recommendation for fitting a fuel filter in the flexible pipe up to the pump or will the standard in line plastic jobbie do?

Peter
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Old 10-08-11, 12:14 PM
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Very interesting. For my 401 I'd like to start with a quick overhaul of my AC fuel pump, but before I even open the glass bowl would like to have all the gaskets in my hand. I have a Bristol workshop parts list but that only gives Bristol part numbers. It is an AC pump but it seems I need to know more before getting parts, ie is it a model U or P or F or somesuch. Does anyone happen to know which model it is & where I might get the gaskets from (I'm in Somerset). I don't seem ablew to make out its model by looking at it, and prefer not to take it off for a closer inspection ... but may have to of course.
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Old 10-08-11, 05:38 PM
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Default Fuel starvation (403)

Inracing in Nottingham does a repair kit for the Bristol fuel pump (along with a wonderful - or frightening, depending on your finances - range of other engine parts) at https://www.inracing.co.uk/RACING_CA..._Engine_Parts/.
Mine came with a variety of gaskets and sealing rings which included ones to fit my 100 series engine OK.
The kit is fairly cheap, but the postage is expensive.
Hugh
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Old 11-08-11, 11:39 AM
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Many thanks Hugh, I have emailed them.
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Old 12-08-11, 05:27 PM
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Default Brass to copper

On the statement that a plumber advised that soldering brass to copper is problematic: Brass is merely copper alloyed with zinc. They solder together quite well. Plumbers use soft solder only, which will still work. Hard soldering is brazing with brass rod or even silver, and is the best as it is at a higher temp and will not decay. The copper must be very clean, as it oxidizes quite fast.
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Old 12-08-11, 07:49 PM
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You are right James. VAT & postage pretty well doubled the cost.

I used plumbers solder on the ferrule and when I soldered some brake pipe into the brass pipe this evening. Not bothered about the reduced capacity as it will suck up on the reserve pipe too.

Removing the fuel pump is very simple. Disconnect the fuel pipe unions (checking that they are still intact, of course!), undo the two nuts below the pump and pull away.

Perhaps I will have a working Bristol again tomorrow. Would RTV silicon or Hylomar be better for sealing the reserve unit onto the fuel tank?
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