DSE, hunting at idle

Just rebuilt my injector pump as it was starting to look a little damp. Used a genuine Bosch seal kit, I'm familiar with this pump VP37 done quite a few in my time.

I did mark the relation of body of pump to EDC to realign properly all other seals went on smoothly.

Timed up with micrometer, just a little advanced from factory which is to be expected due to timing chain stretch, when it initially started with out manifold did move pump to factory mark but still hunting so went back to my timed setting

Had a bit of trouble getting injector lines to prime but freshly charged battery this morning and sprang into life.

But it hunts now at idle, I gave it a 20 mile run to warm up properly and driving really nicely but still hunting, removed connection to timing chatter solenoid and hard diesel knock started so it's working.

Using Nanocom read the fault codes none found after i cleared the one from running with boost sensor disconnected. all live running setting seem about right but erratic with the idle. did play with idle setting up and down made no difference so reset to 128


Any ideas??

Chain stretch will retard timing not advance it. Would say pump top is in wrong place. You need to fit it nipped on a couple of bolts then tap it back and forth until you get a rock steady 750 RPM. Or you have damaged the fuel quantity servo pot. What is the timing modulation on Nanocom? There is no factory mark on pump.

Factory mark is the one I made before removal, always good to have a datum point

Yes chain stretch retards I have advanced it from the factory mark using micrometer, I didn't make it totally clear when I wrote it, Sorry

I broke fuel feed of filter just by knocking it lightly, very brittle but left a stub so put banjo on pump and fitted a bit of rubber pipe,

I resealed the connection as I wasn't happy with it and just got back from Tesco and happy to report it's back to normal, so air after all, I started to look to deeply forgetting the basics

I did wonder about pump top but mark it clearly on all sides to get precisely back where it was, I was told off on another forum as drilling and pinning is safest way, Ive done 10 or more VP37 and VP36 and never had a problem

Timing modulation is pretty steady around 48 which I read is correct it was 70ish before

Thanks for responding

Mamasbigtruck said:

Factory mark is the one I made before removal, always good to have a datum point

Yes chain stretch retards I have advanced it from the factory mark using micrometer, I didn't make it totally clear when I wrote it, Sorry

I broke fuel feed of filter just by knocking it lightly, very brittle but left a stub so put banjo on pump and fitted a bit of rubber pipe,

I resealed the connection as I wasn't happy with it and just got back from Tesco and happy to report it's back to normal, so air after all, I started to look to deeply forgetting the basics

I did wonder about pump top but mark it clearly on all sides to get precisely back where it was, I was told off on another forum as drilling and pinning is safest way, Ive done 10 or more VP37 and VP36 and never had a problem

Timing modulation is pretty steady around 48 which I read is correct it was 70ish before

Thanks for responding

Click to expand...

Static timing is fine then. When pump top is removed you lose the relationship of the quantity servo rest position to the quantity collar. A few thou back or forth will make a difference to the tick over. What is it idling at? Should be a rock steady 750 RPM.

It shows approx 750, not read the figure off Nanocom just rev counter

It has always had a stutter at low RPM say 1500rpm and high gear at light throttle and it's still there, never worked it out. Maybe the Dual mass fluctuations I read about

I may experiment and move top if idle is not 750 steady with setting in nano at 128 my marks are clear so I can move back easily, reading the VW TDI forums they adjust them all the time. I can get a feeler gauge in between top and moulding on pump so can tap it along in small increments

Nothing ventured.........

May live to regret it but at least the pump is easy to get to

Adjusted pump top today as last night from a cold start the idle was rough and didn't smooth up, looking through Nanocom the crank rpm and needle lift rpm were massively different fearing I'd busted the expensive injector it still move pump top suddenly hit the sweet spot idle 750 solid and the two RPM figures matched, running like a turbine so smooth. Obviously now I have adjusted out by luck pump wear

I had been warned by a chap called HC11 (Bosch pump guru) off the vegetableoildiesel forum how precisely the top needs to be aligned but when you can hear engine note change when torquing up each bolt it puts it into perspective.

So thanks Wammers you've helped me again.

Mamasbigtruck said:

Adjusted pump top today as last night from a cold start the idle was rough and didn't smooth up, looking through Nanocom the crank rpm and needle lift rpm were massively different fearing I'd busted the expensive injector it still move pump top suddenly hit the sweet spot idle 750 solid and the two RPM figures matched, running like a turbine so smooth. Obviously now I have adjusted out by luck pump wear

I had been warned by a chap called HC11 (Bosch pump guru) off the vegetableoildiesel forum how precisely the top needs to be aligned but when you can hear engine note change when torquing up each bolt it puts it into perspective.

So thanks Wammers you've helped me again.

Click to expand...

No luck attached to it. Remember what you did for future reference. You have learned something.