Diesel fuel starvation just after starting

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Edward George

Member
Posts
43
Location
Fife
The 5 main bearing 2,25 diesel from a Series 3 that’s fitted in my Series 2A has had fuel problems for the past couple of months when starting from cold. It starts almost straight away each day from cold with some heat applied but stops after about 4 seconds. It then turns over for ages with no exhaust smoke then fires for a couple of seconds and dies. This repeats say a couple more times then it starts and continues to run. If I then stop the engine it starts again immediately without problems. I don’t encounter further problems on repeated starting during the day but the following day the same problem occurs. The lift pump is fairly new. When I try to bleed the injector pump manually before attempting a cold start, fuel comes out of the opened bleed on the main body after several pumps but not then out of the opened bleed on the governor box. However when the engine is running correctly and on opening each pump bleed in turn, fuel spurts out.

I’ve checked all the fuel connections, re-annealed all copper washers and taken the top off the lift pump to check the two valves. I didn’t examine the diaphragm closely but the holding screws were all tight. I’ve check/tightened the two acorn nuts for the governor cover and the gasket looks OK. The injector pump itself was specialist reconditioned about a year ago. There is no sign of fuel leaking anywhere. I haven’t checked the non return valve at the bottom of the injector pump where there is a fuel pipe connection to one of two output connections from the lift pump. The other lift pump output connection goes to the fuel filter. It is as if overnight the fuel is draining from the injector pump and air is getting in. What are the most likely causes?
 
Edward George said:
The 5 main bearing 2,25 diesel from a Series 3 that’s fitted in my Series 2A has had fuel problems for the past couple of months when starting from cold. It starts almost straight away each day from cold with some heat applied but stops after about 4 seconds. It then turns over for ages with no exhaust smoke then fires for a couple of seconds and dies. This repeats say a couple more times then it starts and continues to run. If I then stop the engine it starts again immediately without problems. I don’t encounter further problems on repeated starting during the day but the following day the same problem occurs. The lift pump is fairly new. When I try to bleed the injector pump manually before attempting a cold start, fuel comes out of the opened bleed on the main body after several pumps but not then out of the opened bleed on the governor box. However when the engine is running correctly and on opening each pump bleed in turn, fuel spurts out.

I’ve checked all the fuel connections, re-annealed all copper washers and taken the top off the lift pump to check the two valves. I didn’t examine the diaphragm closely but the holding screws were all tight. I’ve check/tightened the two acorn nuts for the governor cover and the gasket looks OK. The injector pump itself was specialist reconditioned about a year ago. There is no sign of fuel leaking anywhere. I haven’t checked the non return valve at the bottom of the injector pump where there is a fuel pipe connection to one of two output connections from the lift pump. The other lift pump output connection goes to the fuel filter. It is as if overnight the fuel is draining from the injector pump and air is getting in. What are the most likely causes?
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Might be worth having a look at the unit on top of the fuel tank, where the fuel line to the lift pump comes out.
Problems with bleeding the fuel system on a stationary engine are often associated with the lift pump, as above^^^^^^.

Are you using a quality fuel filter? I find Delphi are the best.
 
Can you substitute pipe with some clear hose to check for bubbles , I had problems early on with the leak off pipes and would conk out after a few miles lots of washer changing and new part sorted it
 
Thanks for the suggestions. I’ve ordered a genuine LR lift pump repair kit. Perhaps the diaphragm is faulty or not sealing properly. The filter is yellow and marked JCB. I’ll try for a good quality replacement and check seals. I’m not sure what the purpose is of the non return valve I mentioned at the base of the injector pump and whether a malfunction there would have this effect. Does anyone know its purpose?
 
Edward George said:
Thanks for the suggestions. I’ve ordered a genuine LR lift pump repair kit. Perhaps the diaphragm is faulty or not sealing properly. The filter is yellow and marked JCB. I’ll try for a good quality replacement and check seals. I’m not sure what the purpose is of the non return valve I mentioned at the base of the injector pump and whether a malfunction there would have this effect. Does anyone know its purpose?
Click to expand...
Just to prevent fuel draining out of the low pressure side of the pump, and prevent any contamination entering the pump.

A couple of other things that are worth looking at. In the uppermost banjo union on the filter, there will be a small hole in the brass bolt that goes through the banjo. Check that the tiny hole is not blocked. There is also often a non return valve on one of the filter unions, it is not always present, but if it is, check that it is not blocked, and works.
 
Thanks Turboman. I’ll check the banjo bolt when I change the filter. I don’t remember seeing a non-return valve at the filter but will check. I’ve checked the tank connection but all seems tight with the hose in good condition. If no improvement I’ll source some clear pipe as steve2286w suggests, bleed the system then check for bubbles the following day.
 
That hole in the banjo for the leak off it about 0.010" so its takes some finding, at first sight it looks like there isn't one.
I had a similar problem and in my case is was hard seals in the DPA pump. The pump was weeping when running but letting air in when parked. It began as a small leak and was lost in the oil mess under the sump.
 
rob1miles said:
That hole in the banjo for the leak off it about 0.010" so its takes some finding, at first sight it looks like there isn't one.
I had a similar problem and in my case is was hard seals in the DPA pump. The pump was weeping when running but letting air in when parked. It began as a small leak and was lost in the oil mess under the sump.
Click to expand...
The hole is small, that is why it blocks easily. Usually, in my experience, by residues from when people have been mixing cooking oil in the fuel.
 
Thank you for the further comments.
Excuse my ignorance but what is the purpose of the small hole in the banjo bolt? If the hole gets blocked, what effect does that have on the fuel system?
 
Edward George said:
Thank you for the further comments.
Excuse my ignorance but what is the purpose of the small hole in the banjo bolt? If the hole gets blocked, what effect does that have on the fuel system?
Click to expand...
I might have known that 40 years ago, not sure if I can remember now! :D

I think it might be to allow equalisation of pressure between fuel returning from the injector leak off pipe, and the fuel returning to the tank via the filter head.

But overthinking of it is not necessary to get the engine going, these are pretty simple systems, and so long as everything is plumbed up properly, no leaks, or air entering the system, and a good lift pump and injection pump, it should start up and run.
 
I recently had cause to answer that question. My Perkins has a flame heater fueled from the return line and it wasn't working. I while back I swapped the filter unit just because I had a newer one handy. What I didn't realise was that the banjo bolt I fitted was a std one not the tiny hole one. When I parked fuel was siphoning back to the tank down the return line and air was getting in. It took a while trying to work out and it was only when I compared the old and "new" banjo bolts that it made sense. That tiny hole lets air out easily to bleed the system but it only lets fuel out slowly if at all. Its too small to let the return line fuel syphon back to the tank and create a vacuum at the injector pump. What I can say is having that little hole had a direct effect on reducing how much the engine cranked before it fired.
 
Thanks rob1miles. An interesting piece of information.
Today I replaced the fuel filter with a Delphi one as you suggested Turboman. I also replaced all the seals. I checked the banjo bolt and there was indeed a tiny hole which I pushed a fine strand of electrical wire through to confirm it wasn’t choked. I re-annealed various copper washers. I undid the non return valve at the base of the injector pump to confirm that it was working properly. I took the top off the lift pump to check the diaphragm which appeared to be OK though it seemed a bit wet with diesel underneath. However when I started to manually prime the new filter there was air bubbling out the bleed union on the top. I then realised that my hand operating the lift pump lever was getting wet with diesel. So I think the lift pump which was a cheap replacement has failed as tottot suggested and is hopefully the cause of the original problem. I’ve ordered an OEM replacement from Turners together with a good quality rear crankshaft oil seal which is my next maintenance task to stem a developing oil leak. Hopefully I’ll get the new lift pump fitted next week, then be able to provide a further update. Meantime thank you for all contributions.
 
Success at last!
On Friday I fitted the replacement lift pump from Turners, bled the system and got the engine started. While the engine was running I checked out all the fuel lines and found two minor leaks. One was in a pipe join partway between the filter and top of the injector pump. The other was at the banjo where the same feed pipe connected to the injector pump. Although I had annealed the copper washers, I was still not getting a good seal. I replaced the washers with new ones and applied a very thin smear of gasket jointing fluid. Yesterday evening the engine started and ran continuously.
Many thanks to all who made suggestions and helped me to a solution.
 
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