Help - Search - Members - Calendar
Full Version: Stock D-jet 1,7 running wery lean but why? S O L V E D
914World.com > The 914 Forums > 914World Garage
larss
Have some problems with a stock 1,7 D-jet that runs wery lean, hunts and pops in the intake, hardly running at all....reving up wery uneven and slowly.

-Engine has not been running for severeal years so there is no history to tell.
-Timing triple checked 27 degrees at 3500rpm
-Fuel pressure triple checked 31psi
-All 4 injectors new (repro)
-Trigger points checked OK
-Changed to anoter MPS (which runs well in another d-jet) with no difference
-Changed head temp sensor with no difference
-Compression tested, even around 145psi
-Points, condenser, cap, cables are new (also tested with an old set but no difference)
-All injectors getting pulses, checked and injector plugs are at the correct injectors
-Yes firing order is triple checked

The only way to get it running quite OK is to replace the head temp sensor with a potentiometer at 3Kohms, runs quite good with that even when warm.
This leads me to think that it is running w e r y lean for some reason.

Any ideas?

/Lars S
JeffBowlsby
Which MPS part number do you have, does it hold vacuum and has it been previously adjusted?
larss
QUOTE(JeffBowlsby @ Jul 9 2019, 09:32 PM) *

Which MPS part number do you have, does it hold vacuum and has it been previously adjusted?


Thanks Jeff!
Sorry but the car is not neraby so I can not check tne MPS no at the moment but both MPS we have tested holds vacuum perfectely and still have the epoxi plugs and one of the MPS is borrowed from a car which runs good.

I dont know if I shall trust the new injectors flow rate beeing the same as the original yellow ones. They are bought as beeing a direct replacement however.


//Lars S
BillC
Have you checked for a vacuum leak (or leaks)? Since you already tried a different MPS, looking for leaks is the next thing to check.

If the vacuum and intake hoses haven't been replaced in a while, start there. Also, check the intake manifold (the sheet metal piece that the throttle body mounts to) to make sure there are no rust pinholes in the bottom (fairly common problem, especially when the car sits for a while).
larss
QUOTE(BillC @ Jul 10 2019, 06:21 PM) *

Have you checked for a vacuum leak (or leaks)? Since you already tried a different MPS, looking for leaks is the next thing to check.

If the vacuum and intake hoses haven't been replaced in a while, start there. Also, check the intake manifold (the sheet metal piece that the throttle body mounts to) to make sure there are no rust pinholes in the bottom (fairly common problem, especially when the car sits for a while).



Thanks BillC!
The hoses are all new and checked but as you mention vacuum leaks I suspect the PCV to feed a bit to much air...will check on that the next visit.


/Lars S


/


larss
Short work on the engine today again...
Found out that the PCV was fully open all the time replaced it with a fixed 3mm orifice, idle came down a lot, now idles at 700rpm...but it didnt make any difference on the running, still wery lean, bucks and hesitates a lot when reving up, it can take some 5sec for reving up when opening the throttle.

Checked the throttle switch again, it gives about injector 20 pulses from closed to open and is well adjusted.

We ran it fully warm and adjusted the potentiometer (which we have replaced the head temp sensor with) so that it ran with good response. We must have the pot. on about 3kOhm, much less than that and it wil hesitate. 3kOhm corresponds to a dead cold engine!

Something is making the mixture way to lean but what?

(Sorry Jeff did not get the MPS no this time).

/Lars S
JeffBowlsby
Besides the lean condition, are your distributor weights lubed and vacuum advance working?
larss
QUOTE(JeffBowlsby @ Jul 11 2019, 05:32 PM) *

Besides the lean condition, are your distributor weights lubed and vacuum advance working?


Thanks Jeff,
Yes can see the marks moving to the rpms.รค
Have it spot on 27 degrees at 3500...no vacuim


/Lars
JeffBowlsby
I was not asking about your ignition timing settings, but are your vacuum and mechanical advance functions working? If not it may be a reason for the lag in revving.
larss
QUOTE(JeffBowlsby @ Jul 11 2019, 06:07 PM) *

I was not asking about your ignition timing settings, but are your vacuum and mechanical advance functions working? If not it may be a reason for the lag in revving.


Excuse me Jeff!
Vacuum advance working, checked by sucking.
Rpm advance checked by strobo.

Lars S
larss
A late update on this....wow finally the car is running good! smile.gif

After lots of trobleshooting I swapped the four new injectors (China made) which were fitted for a set of old yellow Bosch and the little 1.7 runs great!
The china injectors were bought as a direct replacement for the Bosch ones but simply do not deliver enough fuel.

However I will not diss the china ones until they are tested and cleaned at an expert shop. There is a small possibility that they are clogged (the car has been sitting for 10th of years and the in car fuel tubes were not flushed before starting the engine but every other hose is new).

I know many others are using them with good result, is there anyone with an opinion on these injectors (FJ114)?.


/Lars S
larss
Final update - short story:
I had a long sitting 1,7 D-jet with new set of (FR114) injectors started and it ran very very lean...when I changed to a set of Bosch injectors it ran great so i suspected the new injectors to be faulty.

However it turned ot that the new injectors only were clogged, probably by old dirt the in car fuel lines (rest of the fuel system is new/cleaned).
After ultra sonic cleaning of the new injectors the 1,7 runs great an I have no reason to doubt the function and quality of the FR114 injectors! smile.gif


//Lars S
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2019 Invision Power Services, Inc.