More FI Questions

[Dave Bell]

O.K.. here we go with more data on the FI/Idle dance.


First a review____________________________
To Date What I have checked on the 75, 1.8L, L-Jetronic.

Intake Air Sensor - Resistance checked O.K.

Throttle Switch - Checked O.K.

Aux Air Regulator - Checked O.K. Watched the Air passage closed while it heated up.

Cylinder Head Temp Sensor - Checked O.K. and added the dash mounted Potentiometer in series for "tuning" purposes.

Decel Valve - Vacuum working on deceleration

All valve clearances Set to spec, new points, set point gap and dwell. Found that I have a distributor from a Type-1 Engine.

Cleaned out throttle body, renewed vacuum hoses... sealed up anything I thought might be leaking.
___________________________________

O.K. that is the review

Now today I checked the fuel pressure:

Follow Haynes, detach vacuum hose to regulator, Key on, flip the stator flap.... pump comes on and pressure goes to 38 lbs while pump is running and drops to 34 lbs when the pump turns off.

I don't hear the pump running for the usual few seconds when I first turn the key before start up and there is 0 pressure before the stator flap is moved.... I can hear the relay click, (relay under the battery),... and the pump run when the stator is flipped... hmmm

Reconnected the air filter assembly and ran the engine with the fuel pressure gauge still attached... seems to pretty much hold steady at about 38 lbs.

To high for Haynes 35 lb. spec, but my idle still drops out sometimes after the car is warmed up.... especially sitting at a light... so on these occasions I dial in more fuel with the dash mounted pot to compensate.

Looked at injectors on cylinders 1&2... black plastic with Part number 280-150-102
Pelican Part number is 280-150-112.. What do I have in there?.. anybody know.

Looked at injectors on cylinders 3&4.... can't see any numbers but they are turquoise blue toward the outside end of them... Is this right?

Things I have not checked:
- Fuel Injection Trigger Points
- Intake Manifold Hoses or Intake Manifold Gaskets Leaking?

Still stumped by this idle thing.... any helpful responses out there?

- Dave


[This message has been edited by Dave Bell (edited 04-15-2000).]

[7391417]

I would replace the fuel injection points. I had a problem with sporadic idle and slight miss at different RPM's. I replaced all sorts of fuel injection stuff and the trigger points was the last thing I did. The new points make the car run so well.

-Brent

[Dave at Pelican Parts]

Well, there *are* no FI trigger points on an L-jet system. The ignition points serve that purpose.

The L-jet system does not have the ~1 second "buzz" of the fuel pump before the motor starts cranking. The fuel pump only runs when the air flow meter flap is moved.

I cannot find a listing for the "102" part number injectors in my Bosch book. The "112" blue ones are the correct ones.

Run the car until the idle bogs down, and let it run that way for ~5 minutes. Shut it off and pull the plugs to check the deposits. Black and sooty is rich, grey/white is lean, tan/brown is good.

That will at least give you an idea of where to start looking.

--DD

[7391417]

Well Dave I learn something new every day, I had know idea that the L-jet did not have fuel injection trigger points.

-Brent

[Dave Bell]

O.K. D.D. -

I let the engine idle low for 5 minutes and then checked the plugs.

On all, the outside conductor looked grey with a hint of white and tan. The ceramic surrounding the inside conductor had a tan deposit... They looked real good to me.

Rechecked the dwell... running about 56 degrees, still inside Haynes wear spec but high. Pushing the RPM up to 3500 RPM the dwell drops to about 50-52 degrees... Haynes says this means a worn distributor.... but I don't expect this to affect my idle.

I reset everything to an idle sitting in the garage of about 1000 rpm, went out for a spin on the freeway, out about 3 miles and off at the first off ramp. At the stop sign the engine settles into an idle of about 1500 RPM. Back home and the idle drops to about 1000 RPM... back into the garage and the idle drops to about 400 - 500 RPM and is stumbling along... I have the dwell meter hooked up again now.... This is a perfect example the the wandering idle problem I have had since I bought the car 1 year ago. (All during this time, my dash mounted pot in series with the Temp II sensor is not adding any resistance to the circuit.. i.e. stock operating mode).

I let this run for about 5 minutes, then turn off the engine and check on the #2 plug... looks good, just like it did on the first check.

Start it up again....I can open the idle screw 1/2 to a full turn and nothing happens until I pop the throttle and then the idle settles to a higher value.... Then close the idle screw 1/2 to a full turn and not much change untile I pop the throttle again and I settle to a little lower idle speed...

There just seems to be know way to predict what the idle point will be in the range of 500 to 1500 RPM and I get stumbling of the engine below 1000 RPM.

Any more advice D.D.?... or anyone else...... should I invest in an MSD electronic ignition?

Oh yes and I almost forgot... I rechecked the injectors on cylinders 1 & 2 to see if I had miss-read them... no, they really read 280-150-102... and after getting out an inspection mirror, the blue capped injectors on cylinder 3 & 4 read 280-150-112 as expected. I still would like to know about those "102" injectors.

- Dave


[This message has been edited by Dave Bell (edited 04-16-2000).]

[This message has been edited by Dave Bell (edited 04-16-2000).]

[RRRCR]

I have a '75 and I was having some FI problems.The injectors were pulled and they had the "102". We were trying different ideas, so I bought a used set from a guy parting out a '75, guess what? "102".Wes said 102 might just be an old part no. or something. Don't know alot but if you have any questions just e-mail.

[Dave Bell]

Thanks RRRCR -

I have since solved most of my idle problems.... found the air bypass adjustment in the air flow meter... it had been set to super lean by the smog guy. Dialed that in and it solved most of the problems.

Since I have both 102 and 112 injectors in my car I have still been eyeing those #102 injectors with some suspicion.... so it is somewhat comforting to know that they have appeared in other 75 cars.

- Dave

[JP Noonan]

Did you check to see if the air-flow meter vanes sticks anywhere in it's arc of travel? Maybe it is sticking and that is why the idle fluxuates, depending on where it gets stuck.

[Dave Bell]

Thanks J.P.

The idle is running very well now after a few minutes of driving... still some roughness during the warmup period.

The sticky flap in the air sensor SEEMS to be an unrelated problem, I have had the air sensor out and I could only get it to stick when it was at the end of its travel in the full open or full throttle position. When this occurs, the mixture of course goes way rich and it is an event you can really recognize... and it is very different from my rough idle during warmup... but this has only happened occasionaly.

The other day I caught it stuck open, pulled into my garage, turned the engine off, then put the key back to the on position... the fuel pump was running, (should not have been), then wapped the top of the air sensor with my hand, and I could hear the flap fall back and the pump then turned off.

Already put out a request for a spare air sensor.

- Dave

[JP Noonan]

Too little too late... I read your other post about the air sensor after I already made the above post...no really I did...seriously I really did. Come on someone beleives me , right?

As far as 914 parts go a new vane sensor is about $170-$190 not THAT bad considering how important it is. Just make sure you figure out how it got bent (usally a backfire through the intake) before a new one gets messed up.