[Vwdiesel] [xjlist] Engine Questions

[Kurt Nolte]

A lift pump isn't going to help you inject more fuel, but it will help 
keep air out of your fuel lines. In the present setup, your injection 
pump is pulling fuel into itself by generating a small vacuum with the 
vane pump. Vacuums don't care how they get filled, only that they get 
filled, and air is easier to flow than relatively viscous diesel. If 
there is a crack in a line somewhere, air will be drawn into the fuel 
line and pushed into the injection pump.

A lift pump would put the fuel lines under positive pressure; no vacuum, 
no leak-in of air. The vane pump still works the same way, moving a 
specific amount of volume each time it rotates, but now it's not drawing 
a vacuum, it's getting filled by the lift pump's positive pressure each 
time the ports are open. If you have cracks in the line, fuel will now 
leak -out-, helping you find them.

-Kurt

Stephen Kraus wrote:
> This one does not have a lift pump
>
> Oh and for those wondering it is a 2.1l Renault Turbo Diesel, finding the
> manual in english is hard as hell.
>
> I suspect it is like most of you have said its probably air in the lines, I
> guess I will just try re-bleeding the injector lines. The thing is, the
> engine will run longer if I give it more fuel, perhaps I should try a lift
> pump
>
>
>
> On Tue, Aug 26, 2008 at 11:59 PM, ernest breakfield <
> ernestb at backyardengineering.org> wrote:
>
>   
>>   hi Jim!
>>
>> i believe you're probably right for most diesels, but i don't think
>> my old Mercedes 617.952 has a lift pump,...
>>
>> cheers!
>> e
>>
>>
>> Jim wrote:
>>     
>>> Diesels have 2 fuel pumps- the injector pump which times and meters the
>>> fuel delivery, which the injector lines come out of; and the lift pump,
>>> which is a high volume, low pressure pump to feed the fuel to the
>>> injection pump. The lift pump is usually mechanical on older diesels,
>>> but could be electric. Usually its a mechanical pump mounted to the side
>>> of the block somewhere. The fuel feeds from the tank to the engine, in
>>> through the lift pump, then through the fuel filter, then to the
>>> injection pump.
>>>
>>> As for the turbo, a diesel will run just fine without the turbo,
>>> especially at idle. It just won't have the power, and like Neal said,
>>> will run rich. This will be seen by black smoke out the exhaust. You
>>> also don't want to drive like this, because the exhaust temps can get
>>> very high...you don't want to melt a piston.
>>>
>>> If you just assembled the engine, did you bleed the fuel system? Start
>>> the engine (or aty least have someone crank it, if it won't start) and
>>> loosen the first bleeder screw in line- there is usually one on top of
>>> the fuel filter housing. Just crank it loose a hair and let any air come
>>> out. If you just get a nice constant supply of fuel, close it up. Next
>>> bleed the lines. Where the lines attach to the injectors, loosen the
>>> fitting on the first injector, and let any air out until you just get
>>> nice fuel. Snug it up and move on to the next injector, until you have
>>> done all of them. Most injectors won't fire if they have air behind them.
>>>
>>> Jim
>>>
>>> Neal Hoover wrote:
>>>       
>>>> is yours a mechanical fuel pump or electrical? those thing have to be
>>>> timed
>>>> just right so fuel is injected precisely when it needs to be.
>>>> do you have a factory service manual for that motor?
>>>> that's where i'd start.
>>>>
>>>> Neal A. Hoover
>>>> Project '76 J-10
>>>> Project '96 XJ
>>>> http://community.webshots.com/user/proj96xj
>>>>         
>>> <http://community.webshots.com/user/proj96xj>
>>>       
>>>> <http://community.webshots.com/user/proj96xj
>>>>         
>>> <http://community.webshots.com/user/proj96xj>>
>>>       
>>>> ----- Original Message -----
>>>> From: "Stephen Kraus" <UB3RATL4Sf00 at gmail.com<UB3RATL4Sf00%40gmail.com>
>>>>         
>>> <mailto:UB3RATL4Sf00%40gmail.com <UB3RATL4Sf00%2540gmail.com>>
>>>       
>>>> <mailto:UB3RATL4Sf00%40gmail.com <UB3RATL4Sf00%2540gmail.com>>>
>>>> To: <vwdiesel at vwfans.com <vwdiesel%40vwfans.com> <mailto:
>>>>         
>> vwdiesel%40vwfans.com <vwdiesel%2540vwfans.com>>
>>     
>>> <mailto:vwdiesel%40vwfans.com <vwdiesel%2540vwfans.com>>>;
>>>       
>>>> <xjlist at yahoogroups.com <xjlist%40yahoogroups.com> <mailto:
>>>>         
>> xjlist%40yahoogroups.com <xjlist%2540yahoogroups.com>>
>>     
>>> <mailto:xjlist%40yahoogroups.com <xjlist%2540yahoogroups.com>>>
>>>       
>>>> Sent: Tuesday, August 26, 2008 4:32 PM
>>>> Subject: [xjlist] Engine Questions
>>>>
>>>>         
>>>>> I have nearly completed the 2.1l Turbo Diesel I am putting in the
>>>>>           
>>>> Jeep, I
>>>>         
>>>>> have a couple questions:
>>>>>
>>>>> Should the lack of the turbo keep the engine from running
>>>>>           
>>> constantly? I
>>>       
>>>> can
>>>>         
>>>>> get the engine started and it fires up but it acts like its choking,
>>>>>           
>>>> slows
>>>>         
>>>>> down, and then stops firing. The longest I've gotten the engine to
>>>>>           
>>> hold
>>>       
>>>> for
>>>>         
>>>>> is about 30 seconds to a minute, that is without the turbo. I don't
>>>>>           
>>>> have a
>>>>         
>>>>> reliable hose made to port the turbo air to the air intake yet.
>>>>>
>>>>> Mike Strawbridge been a big help in both the headgasket job and
>>>>>           
>>>> torqueing
>>>>         
>>>>> down the head (and letting me make a horrible mess of his garage)
>>>>>
>>>>> I'm posting this to both the VW diesel list and the Jeep list
>>>>>           
>>>> because I'm
>>>>         
>>>>> hoping with all the answers I get I should be able to piece together
>>>>>           
>>>> what
>>>> I
>>>>         
>>>>> need to do. I just want to remove that damned 2.8l V6
>>>>>
>>>>> --
>>>>>