Diesel Problems

[pycoed]

See through pipe is handy for this job, can look for bubbles

+1 Replace the leak off pipes with clear tube & see if you have bubbles. If you do, have a good scrape around on top of the tank where the feed & return pipes enter it.
Does it so it when parked facing downhill? My pickup was fine facing downhill but need 30secs of cranking to start if facing the other way (Merc OM662 engine in SSangyong)

On these & other Merc engines there are O rings on the outlet valves of the injector pump which can be fairly easily replaced. Usually show up as dampness on top of the pump, but mine didn't show at all. I have no idea whether Cummins engines use the same system, but some Googling may turn up something?

 

[Massey_3115]

To educate my nugget of a brain, if you run something out of diesel, or change filters etc you need to bleed.. So if the diesel has run back and air has got in, why does it not need bleeding to start after 20 secs of cranking etc?? because the air is forced back out through the hole where it is leaking ??

 

[Mursal]

Yes, or a better way to think of it, the diesel is forced through the return pipe back to the tank.
After changing the filter if you had a big enough battery and starter system fit for 10 minutes constant running, you wouldn't have to bleed anything.

 

[multi power]

Isn't there a fair amount of difference between a little fuel running back and an empty system?
I seldom see much success just cranking over, good fast tow much better

 

[multi power]

A good idea before changing filters is fill with fuel first
Also crack off a injector pipe

 

[Ley253]

Had this type of thing many times over the years. Quick cure is a non return valve near the tank, they are only a few pounds from diesel shops. The problem is fuel running back to the tank, and that can be caused by a multitude of things, the leak off line finishing above the fuel level in the tank is one, its fine when the system is new, but not when the valves etc get past their best.Air is drawn in through this, allowing the fuel to run back. Another is the filter head on filters using the 296 element.These valves can often give a damaged lift pump a new lease of life. Valves in the pump fail,or drop out. Fitting a non return in the suction line in effect replaces the valves in the pump. I used to carry these valves in my van when working as a lift truck engineer.

 

[roscoe erf]

Yes, or a better way to think of it, the diesel is forced through the return pipe back to the tank.
After changing the filter if you had a big enough battery and starter system fit for 10 minutes constant running, you wouldn't have to bleed anything.

or a can of sniff

 

[Ley253]

Be

or a can of sniff

best make sure any glow plugs are disconnected though, otherwise results are "entertaining"

 

[John 1594]

Be

best make sure any glow plugs are disconnected though, otherwise results are "entertaining"

usually stuffs the headgasket. Especially on "paired" bore engines, where the gap between 1/2 and 3/4 is very small, more often than not the detonation caused by the ether when ignited by the glowplug will blow the gasket clean through between the bores, as this is the weakest point in the gasket

 

[Ley253]

usually stuffs the headgasket. Especially on "paired" bore engines, where the gap between 1/2 and 3/4 is very small, more often than not the detonation caused by the ether when ignited by the glowplug will blow the gasket clean through between the bores, as this is the weakest point in the gasket

Turns the paper air filter into wedding litter as well, usually with interesting sound effects.

 

[DrWazzock]

Remember fuel will run back even if the air leak is on the fuel return side. I'd replace all of the flexible tubes for starters as they harden and don't seal after a few years. Then start looking for cracks in metal pipes and fittings. Provided air can't get in anywhere round the loop, then it should never run back.

 

[borderterribles]

Is the lift pump mounted on the rear end of the diesel tank? I'm on my fifth DAF, the first four were so reliable, I couldn't tell you where their lift pumps were. All regularly serviced, filters changed etc, and never a problem. The latest one has been more trouble, diesel-wise than all the others put together. The tank mounted lift pumps are notorious for drawing air round the plastic plunger and causing fuel problems. Just had my second new lift pump since August!

 

[Ley253]

Is the lift pump mounted on the rear end of the diesel tank? I'm on my fifth DAF, the first four were so reliable, I couldn't tell you where their lift pumps were. All regularly serviced, filters changed etc, and never a problem. The latest one has been more trouble, diesel-wise than all the others put together. The tank mounted lift pumps are notorious for drawing air round the plastic plunger and causing fuel problems. Just had my second new lift pump since August!

Time to fit an in line one then facet do one I believe

 

[John 1594]

Remember fuel will run back even if the air leak is on the fuel return side. I'd replace all of the flexible tubes for starters as they harden and don't seal after a few years. Then start looking for cracks in metal pipes and fittings. Provided air can't get in anywhere round the loop, then it should never run back.

Had that happen when someone replaced the leak off pipe beween the injector rail and the tank

original pipe had a restrictor in it and a double loop. New pipe was a direct route and it siphoned the pump dry overnight!!

 

[Massey_3115]

I think I may have found a possible source of the diesel running back. The pipe is quite loose. Any ideas what the top fitting is? I'd it likely to be a quick 'push' in fitting or a 'olive' type fitting. I've not had a chance to strip out yet, the weekends job!

 

[Mursal]

That may well be a collar the top black nylon pipe is pushed into.
Push collar in and nylon pipe may come out?
Worth drying it well with a rag, just to be sure you have the correct pipe that is actually leaking. As the top one doesn't have diesel dripping off it?

 

[Massey_3115]

The top one was definatley leaking. Have replaced the fitting today so see what tomorrow brings !

 

[Mursal]

Happy days .............

 

[Renaultman]

Looks like the middle one has been braized. Top one looks more like an air line fitting.

 

[Bloders]

the top two, the clamp is off - is that your doing?
if not, they may be vibrating when the truck is going, which could be the cause of the problem?