79 Euro 4.5 injector question

[dave944cab]

Hi,

What should the fuel look like coming form an injector at idle from a 79 k jettronic.

Got the car and started in after lying up for a year or so, there is a miss most of the time up to 3000 rpm and then she goes well,

I have changed the plugs , rotor arm and distrib. cap. now its a little better but the miss is still there. tried ht leads of another 928 and the same.

I am thinking clogged fuel filter ? I took 2 injectors out and ran them into a bottle, it was just dripping out, when revved it does come out in jets but not very even , looks like 3or 4 separate jets not uniform.

Any ideas greatly appreciated.
Dave

[MPDano]

Yeah, old injectors. I had to replace one of mine as when i finally got mine running, it was only running on 7 cylinders. Mine also stumbles a bit on take of but does smooth out at a higher RPM. I was told it could be the Fuel Distributer Plunger. An easy fix but too busy to do it.

[Danglerb]

CIS injectors work by a differential pressure from the fuel side to the spray side. The fuel pressure regulators keep the differential pressure constant by adjusting the fuel pressure to track the intake manifold pressure.

Dripping could be due to leaking if the differential pressure is low and they actually should not have any flow at all,

OR

Poor flow due to clogging or some other issue if the differential pressure is high.

What pressure did you check the injectors with? or exactly how was the test done.

[dave944cab]

I didn't use any gauges, must order some.

The way i tested was i took the injector out and placed in a plastic container, started the car and watched the petrol dribble out.

Can anyone recommend how and where to check the fuel pressure and a good kit that will work.


Thanks all
Dave

[american-kiwi]

get some new injectors...use the "Brass" MB ones..here's the part# Bosch 0437502047...cheap at $22.oo new each,..i have these in my 78....i had the same problem as you....leaking down...no spray etc, now it runs great

[Danglerb]

Originally Posted by dave944cab

I didn't use any gauges, must order some.

The way i tested was i took the injector out and placed in a plastic container, started the car and watched the petrol dribble out.

Can anyone recommend how and where to check the fuel pressure and a good kit that will work.


Thanks all
Dave

I thought you might have done that, trouble is the control pressures are going to be high manifold vacuum (low fuel pressure), but your test injectors are at atmospheric pressure so the fuel pressure ends up about 14 psi too low for any flow.

What you need is about a 4" thick plastic tube that would seal to the injector on top and seal to the injector hole on the bottom.

Or make a functional test rig with a gauge and some way to vary the fuel pressure.

Or just send the injectors out and have them cleaned and flow tested.

Or just buy a new set.

[DPW928]

The spray should be conical regardless of engine speed. Only the pressure varies. JCW sells a CIS test set for around $60. You can try cleaning the old injectors with a product like Gumout or Techron concentrate, but new injectors should be a quick fix and reduce the likelyhood of running too lean and burning a headgasket.

[MPDano]

Originally Posted by american-kiwi

get some new injectors...use the "Brass" MB ones..here's the part# Bosch 0437502047...cheap at $22.oo new each,..i have these in my 78....i had the same problem as you....leaking down...no spray etc, now it runs great

Did yours have that of idle stumble too?

[american-kiwi]

mine were just dumping fuel at WOT all time...even with the dist' plunger closed..i know my dist' was shot...but so were the injectors...no kidding...put 5gl's fuel in it..was empty within 1-2 min's running....washed my rings down too...got them to recover...but i thought my engine was shot for sure...i had 2 good engine fires!!!!...the 2nd one scared the cr@p out of me...lol...thats when i decided enough is enough screwing with a worn out fuel system parts...and bought my setup of Mike
MPDano..car would hardly run at all...yes...rev up...drop off...it was all over the place....after replacing it with Mike's system...runs like a dream now

[Danglerb]

Do you still have the old injectors?

I'm thinking of trying to build some kind of tester, and might buy a cheap set of old injectors to play with.