230ge Engine stutter misfire Jetronic

4 replies [Last post]
Jdring
Jdring's picture
Offline
Joined: 12.04.2004
Location: South of Oxford, UK. 87' 230GE SWB Manual, 89' 230GE SWB Auto, 2012 G350Bluetec LWB
GWOA Groups: Committee, Members

Looking for some details of the fuel and ignition side of a 230GE which starts well and runs smooth but has a regular stutter and misfire when on the road.  The stutter prevents the G progressing to a comfortable cruising speed.

There are a lot of good forum threads on here pointing towards: the Bosch K Jetronic injection "is all about fuel pressure and vacuum pipe airleaks."

Some of the electronics have been renewed (distributor), and there is a new/replacement metal petrol tank and pump. 

But the pump is running continuously.  And on another 230 the pump runs for a few seconds and stops (up to pressure?).  So why is this replacement pump continuing...maybe never getting up to pressure?  how is that detected?  

I found a good generic description of the K Jetronic system (attached), and see that pumps have a pressure relief valve in it that opens and releases fuel back into the inlet side when pressure reaches a high level.  But there should be a switch somewhere to activate the fuel pump relay...how is that working?

And then there is a petrol 'accumulator' which is a device that smooths out the fuel delivery and has a spring and plunger in it to maintain steady pressue to the Jetronic when the pump stops. #130GBP plus for such a little thing.

Maybe the pump is struggling to get fuel flow from the tank due to a blockage?  Or through the Accumulator.  But the engine runs smooth until you get on the road and then in each gear there is the stuttering, faltering behaviour.

Any ideas?

Oh... this G is harder to start when warm.  That apparently points to the Accumulator?

Login or register to view attached files
JASONGDS
JASONGDS's picture
Offline
Joined: 15.07.2011
Location: High Peak
GWOA Groups: Members
Re: 230ge Engine stutter misfire Jetronic

Generally these things are caused by renewing  other parts and upsetting something accidentally,  was the distributor renewed same time as the fuel tank? Have you double checked all the vacuum pipes for cracks etc? 

gav.helme
gav.helme's picture
Offline
Joined: 29.04.2011
Location: North Lincolnshire
GWOA Groups: Members
Re: 230ge Engine stutter misfire Jetronic

Could also be a failed temp sender or dribbling 5th warm up injector 

Could possibly be not shutting off the cold start properly and over fueling when warm ? 

Jdring
Jdring's picture
Offline
Joined: 12.04.2004
Location: South of Oxford, UK. 87' 230GE SWB Manual, 89' 230GE SWB Auto, 2012 G350Bluetec LWB
GWOA Groups: Committee, Members
Re: 230ge Engine stutter misfire Jetronic

So the warm-start issue is often linked to a failed fuel line accumulator, but the stuck/dripping warm up regulator cause is one to check also.

But the main issue is the stutter, or misfire.

We noticed the (new) fuel pump doesn't switch off.  It's supposed to run, pressure the pipeline and cut off.  I know the pumps have a relief valve that lets excess pressure fuel back to the inlet, but then its supposed to stop.  But how would the fuel pump relay know the fuel is at pressure and cut the voltage?  Is there a pressure switch somewhere?

The pump is definitely running though, so checking the flow would be a good thing to do.  It will happily rev when stationary and hold without misfire at 3-4k rpm... so fuel delivery can't be that bad.  Why the misfire when underway.

I'm going to try to look at the wiring diagrams.

Jdring
Jdring's picture
Offline
Joined: 12.04.2004
Location: South of Oxford, UK. 87' 230GE SWB Manual, 89' 230GE SWB Auto, 2012 G350Bluetec LWB
GWOA Groups: Committee, Members
Re: 230ge Engine stutter misfire Jetronic

Update.  One garage looked at it, fiddled with something and made it impossible to start.  Handed it back worse. Muppets.  Once running the stutter is still there, but more intermittent.  Running rich but mechanically seems fine and quite smooth and will hold 70mph ok (5 speed manual)

So, G delivered to Bosch Service Centre for a good look at the K-Jetronic.  Likely replace the fuel pump which never stops (suggests it never really gets the fuel line pressurised).  Maybe replace the fuel accumulator which smooths the pressure and holds it with a non-return valve.   Check the vaccum lines and replace the 230GE breather pipe which connects the rocker cover to the airbox (15cm long - anyone know the part number?).  These always split and crack up with the heat.

The garage won't need it, but I found the following good service guide for those wanting to sort it themselves!

https://tasteslikepetrol.net/2020/02/bosch-k-jetronic-basics/