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Old 20-04-2015, 13:48   #1
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Diesel dies when Idling

Hey all,

I am new to diesels and mine started doing something odd this last weekend.

When idling it died. It tries to turn over just fine and I have already determined it's not electrical. If I hand pump the fuel in, it idles fine. This makes me think something is wrong with the either the vacuum or maybe the filters need bleeding. If I increase the throttle it feeds okay.

However being new to a diesel I am not entirely sure.

Any suggestions and recommendations?

Thanks!
-Caolan.
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Old 20-04-2015, 13:56   #2
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Re: Diesel dies when Idling

Hi!
This happens to me when a fuel filter is nearly clogged.

It spurred me to add a suction gauge to the filter.
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Old 20-04-2015, 16:57   #3
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Re: Diesel dies when Idling

Quote:
Originally Posted by msponer View Post
Hi!
This happens to me when a fuel filter is nearly clogged.

It spurred me to add a suction gauge to the filter.
Fuel suction side is always a good candidate to start with. If you ever have a problem on the pressure side you'll either have a leak or rough running or no running.

Do you have a water trap before the final fuel filter? You always want to know 'my fuel is clean and there is no water or air in my fuel.'

A vacuum gauge will quickly highlight if you have an obstruction on the suction side. It is a visual check so easy to check everytime you stick your head in the engine room. It will also indicate if you have a drainback problem.

I know mine reads 5". At 8" I have an issue and should see a buildup in my Racors. I dont ever want to see 15" because then I'm cavitating on the suction side of my lift pump.

I have 30 micron filters in my tertiary Racor 500s, 10 micron secondary filter in my new Racor P series fuel conditioning module, then my lift pump and a 2 micron filter in my primary filter before my injection pump. You can never have diesel fuel which is too clean.

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Old 21-04-2015, 00:23   #4
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Re: Diesel dies when Idling

Make & model of engine will be of help save writing a book.
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Old 21-04-2015, 10:33   #5
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Re: Diesel dies when Idling

what is the engine, and what is the RPM of your Idle...when it dies...
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Old 21-04-2015, 15:39   #6
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Re: Diesel dies when Idling

Hello every one
I'm new to this site but just thought I'd stick my oar in. I'm going to leave Caolan in the hands of more experienced people. In general terms however I heard there are three things that usually go wrong with a diesel and they are
1) fuel
2) fuel
3) fuel
That is unless its actually broken
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Old 21-04-2015, 21:24   #7
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Re: Diesel dies when Idling

Two questions. First. Is the fuel supplied from below the lift pump or from above the lift (priming) pump? Bleed the system to the injectors then if there is a miniscule hole or seal leak, it will pull in air and diesels don't run on air alone (ah, if only!). This can be checked by setting up a jerry rig from a fuel container that is above the engine and bypasses everything up to the lift pump. If it runs OK then you have an air leak. Fix it.

Second. On many rotary injector pumps, the pump is cooled and lubricated by running excess fuel through the pump. On many Bosch injector pumps this can be seen because any return fuel from the injectors (usually a small diameter tube) joins a larger diameter (usually about quarter inch) return line for the injector cooling/lubricating excess fuel. This larger diameter return is usually on top of the rotary injector pump (there are variations ).

Sometimes, a small rubber seal inside the pump breaks and blocks the outlet causing a build up of fuel pressure inside the injector pump. This will cause the injector pump to stop delivering fuel to the injectors. There are two ways to check this. Examine the fuel flow in the return fuel line from the pump. Minimal fuel returning indicates a blocked outlet inside the injector pump. Another method is to start the engine then quickly open the bleed nut on the side of the pump. Fuel should spill out quickly. Undo it enough to reduce any internal pressure build up, but not enough to starve the injectors. Not a permanent solution! Unfortunately a blocked pump usually means an injector pump overhaul.

A plethora of filters and pumps can increase the chance of air being pulled in. Another issue is that if you have a pump for transferring fuel e.g. from tank to tank or through a filter, that pump may not leak when transferring as the fuel being pumped will help seal the shaft seal (not that it matters here), however, if the pump is still in the fuel circuit when the engine is pulling in fuel, that end seal may allow air in. Solution is to "valve isolate" that pump from the normal engine fuel reticulation.
Best of luck.
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Old 21-04-2015, 23:51   #8
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Re: Diesel dies when Idling

Quote:
Originally Posted by Taswildlife View Post
Hello every one
I'm new to this site but just thought I'd stick my oar in. I'm going to leave Caolan in the hands of more experienced people. In general terms however I heard there are three things that usually go wrong with a diesel and they are
1) fuel
2) fuel
3) fuel
That is unless its actually broken
Hello 'Taswildlife' and welcome to CF.. Are you a Taswegian?

I'm not sure of your saying, seems to me to be the same thing?
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Old 22-04-2015, 06:06   #9
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Re: Diesel dies when Idling

Also check to see if your fuel return line is clear all the way to your tank.A diesel wont run long if the return line is stopped up.
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