2.5 N/A Hunting

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pos

pos

Well-Known Member
Posts
3,685
Location
West Yorkshire
Ayup,

The past couple of weeks (sinse its been a bit colder) my 2.5 N/A is starting up really strange. Basically, I give it 25 seconds on the glowplugs and turn it over and it seems to start straight up, but my accelerator has no effect until it's been "hunting" for about 15 seconds. The engine kind of sounds like it is still trying to start (ie. very quick kind of firing sound and lots of juddering / shaking). Usually I can rev my engine just as soon as it has started to get it up and running as opposed to leaving it cranking, but my accelerator is basically doing nothing! It drives well after about two minutes though.

Any ideas?
-Pos
 
I did have, but not for a months worth of fill ups (2 fill ups). I only ever used to have about 6 litres to 30 litres of diesel anyway. Do you reckon a bottle of redex will do the trick, or is it something else?
 
That's interesting Red, cos I only have to tap my throttle to make it go once its going. Do you suggest that I just slacken it off verry slightly? What exactly is the cold start valve and how does it work?
 
Redhand is on the ball here.
There MUST be slack in the throttle cable, because

1. if not the cold start systems are disabled.
2. the slow running governor is disabled.

Look for a little lever with an adjuster screw and nut, that leans on the fuel inlet at the front end of the injection pump. That lever is the slow running lever.

Loosen the throttle cable till (a) there is some slack but (b) it still gives full throttle when she decks the pedal for you.

Now, with NO THROTTLE, and the engine stopped, the injection pump engages cold start systems (excess fuel and timing) as long as the engine is stopped or turning over at starter-motor speed. So it fires up better.

As soon as it fires up, the slow-running governor should take control and should blast in fuel to get the speed up as quickly as possible to tickover at about 750 rpm or so, and hold it there even in freezing cold conditions.

This will NOT happen if the throttle is pressed or the cable is too tight!

As soon as the engine is running, move the slow running lever out with your fingers, and see how it works. TO warm the engine up fast or have it running at a fast tickover for jump starting or the like just jam a small bit of plastic between the end of the tick-over adjuster screw and the fuel inlet.

The way these injection pumps work is extremely clever, but if we don't adjust them right, or if we operate them wrongly, the systems probably won't engage, and starting up can be very difficult.

CharlesY
 
Just had a look, and their is enough slack in the cable to ensure that the pump is not being 'revved' at all on startup or tickover. The longish bar is right against the adjustable screw which prevents it from loosing revs on tickover. Are you telling me that I need to reduce this even more?

Perhaps my old friend can be of help:
http://www.skuf.co.uk/temp/pump.jpg

Am I right in thinking that the little lever with the adjustable screw near number 7 is the one you are referring to? Should this be up against the fuel inlet pipe or away from it in order for cold start to work?
 
pos said:
Just had a look, and there is enough slack in the cable to ensure that the pump is not being 'revved' at all on startup or tickover. The longish bar is right against the adjustable screw which prevents it from loosing revs on tickover. Are you telling me that I need to reduce this even more?

This lever should have TWO adjusters, one for full throttle (meaning maximum revs will shut it down), and one for NO throttle.
Tickover MUST NOT be set using this adjuster, because this is the main throttle pedal lever! Has the SLOWEST adjuster on this lever been moved at all? It should NEVER be adjusted, even if you take a chance on increasing the maximum revs allowed by moving the high end screw. You must NEVER undo the setting screws of the several parts of the main throttle lever. The way they relate to each other is fairly critical. Have you "adjusted" any of these?

With the engine RUNNING at tick-over speed, and NO throttle, back off the SLOW end adjuster of the main thottle lever. If the engine slows down .... BAD. Keep backing it off till it stops getting slower, then lock it again. Now move the slow running lever. The slightest movement should raise the tickover speed.

Perhaps my old friend can be of help:
http://www.skuf.co.uk/temp/pump.jpg

Am I right in thinking that the little lever with the adjustable screw near number 7 is the one you are referring to? Should this be up against the fuel inlet pipe or away from it in order for cold start to work?
Click to expand...

YES!
This is the slow running lever, and must always be leaning on the fuel inlet pipe which is its stopper. It will not move by itself, ever. The only times it will move is if you adjust it or stick a plastic spacer in it to raise the tickover speed.

You haven't been fiddling with all these have you ?????

CharlesY
 
Oh right! No I haven't been messing about with it. So in order to get my engine to cold start, does this need to be against the fuel inlet pipe or pulled away from it?
 
Have you checked your glow plugs are ok? I had something similar on a 2.5NA 90 years ago and had to replace them, as when starting it would only fir on a couple of cylinders and woudn't pick up untill the others had come on line!
 
pos said:
Oh right! No I haven't been messing about with it. So in order to get my engine to cold start, does this need to be against the fuel inlet pipe or pulled away from it?
Click to expand...

If you leave this well alone it will ALWAYS sit leaning against the fuel inlet.
If it isn't, you've got a problem.

You have been given good advice to pull out the glowplugs. The N/A needs four good hot plugs to be sure of a brisk start on a cold morning.
I would agree - get the glow-plugs good first.

CharlesY
 
Alright thanks! The glowplugs are about 2 months old so they should be like brand new. I'll give them a check though just in case. It did start a little better this morning though, and there's a bottle of redex running through the system now too.
 
Just thought that I'd bring this topic back up because I've adjusted my tickover / engine idle speed with the little adjuster so that it ticks over slightly quicker and thus not shaking my car to bits. Will this stop the cold start from working, or does that have absolutely nothing to do with the cold start working what so ever? I haven't touched the throttle cable

-Pos
 
pos said:
Just thought that I'd bring this topic back up because I've adjusted my tickover / engine idle speed with the little adjuster so that it ticks over slightly quicker and thus not shaking my car to bits. Will this stop the cold start from working, or does that have absolutely nothing to do with the cold start working what so ever? I haven't touched the throttle cable

-Pos
Click to expand...

This will NOT affect the cold start system.

One reason for using a separate lever to control the tickover governor is just that, so the tickover can be set the way you want without affecting the cold start.

CharlesY
 
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