Reving up then cutting out

[Benno 1688]

Hi my bmc 1800 keep reving the normal then Rev up then cutting out. I have changed the fuel filter the cleaned the lift pump gauze. It seems to happen after about two hours running the tempreture is ok and the oil pressure is good. I thought it might be a fuel problem but I'm not sure, if I let it cool down it runs ok for a while. Anyone got any ideas.

[the barnacle]

my first thought was fuel starvation as if after reving the fuel retracts - one reason why on some older engines there is a one way valve in the line.

[RLWP]

It sounds like an air leak into the diesel system. Check all the pipe joints starting at the tank

 

Richard

[Benno 1688]

Tha air leak has been in my thinking. I have checked, but I will check again. This might sound obvious but what the best way of checking.

[RLWP]

Tha air leak has been in my thinking. I have checked, but I will check again. This might sound obvious but what the best way of checking.

 

A pair of spanners on each joint in the line

 

Richard

[The Bagdad Boatman (waits)]

Fuel starvation could be caused by somthing blocking the supply. Use a bike pump to blow the fuel line clean and vacume the crud off the bottom of the tank.

[ditchcrawler]

Hi my bmc 1800 keep reving the normal then Rev up then cutting out. I have changed the fuel filter the cleaned the lift pump gauze. It seems to happen after about two hours running the tempreture is ok and the oil pressure is good. I thought it might be a fuel problem but I'm not sure, if I let it cool down it runs ok for a while. Anyone got any ideas.

Can you restart it without bleeding the fuel system? if so I don't think its air getting in but could be fuel starvation. Anything back tho the bottom of the pickup pipe in the fuel tank.

[Benno 1688]

No I need to bleed the system. I think it could be a leak at the lift pump. It's been a ongoing.

[Tony Brooks]

Most of those lift pumps have a domed cap held on by a single centre bolt. The cap is sealed by a soft washer around the bolt and a "rubber" O ring under the cap.

 

It is too easy to collapse the dome, especially if the seal on the bolt has failed, by over-tightening the bolts. With care it can be re-domed with a ball part of a hammer.

 

I would use a nylon washer around the bolt.

 

The O rings tend to expand so if anyone took it out it can be a beast to get it back and make it seal.

 

I would also be looking at the seals on the fuel filter, especially what seals the filter's centre bolt.

 

 

Anything that reduces the fuel pressure inside the injector pump is likely to cause the revving up so it could be either a blockage or an air leak.

Edited July 9, 2016 by Tony Brooks

[Chalky]

Is there any debris / foreign matter in the tank that could be blocking the pick up? As the pump starts drawing fuel it will create a gentle flow that could draw debris to the pick up. Once the engine is off it can float away and it could appear that there's nothing wrong - till the next time.

 

A colleague of mine had this on a brand new car about 20 years ago. It drove fine for a few hundred miles then would start cutting out. The dealers diagnosed fuel starvation, pulled the pump assembly out of the tank and found a large plastic bung. These were used to protect the tank from debris during assembly and someone had pushed it in instead of removing it. He rang up the appropriate cell manager on the Longbridge line to complain and was heard to utter the words "This bungs a stopper". We never heard the end of the call, the office had collapsed in fits of laughter.

 

Also how old / worn is the engine and how full is oil level - is it above / near the top of the dip stick?

Edited July 9, 2016 by Chalky

[Benno 1688]

The oil level is fine to be honest I have checked most things but never the fuel pick up from the tank. I will look at that next