Engine, Fuel or FI problems, spitting and sputtering again Options

[malcolm2]

75 1911cc with L-jet.

back in January I made this post:

http://www.914world.com/bbs2/index.php?s=&...t&p=2286395

I have been driving quite a bit since then, even took a 6 hour round trip day ride to Knoxville. My guess it 4 or 5 tanks or about 1800 miles and no issues.

Same thing happened today... Driving home from work on the interstate, MPH at 80, revs about 3400. Again, going up a long low hill, not far from my exit. I could feel some spitting and sputtering.

The VDO CHT ring under #3 started heading down. Dropped to 200*F. When I exited and took my foot off the gas, it died. Started right up and I made it home braking with my big toe and gassing with my little toe.

This time, I have a 1/2 a tank of e10 gas (not positive on that). So it is not running empty as hoped last time. Fuel pressure was at 40 on the engine bay gauge.

Other suggestions last time were the filter. I am going to remove that today.

With the #3 temp as it is, I might should start there. I will try my induct timing gun on it to see about spark. Need a noid light for the injector. and i'll take a look at the plug.

I'll remove the disty and take a look. But #3 seems to not be firing and generating heat.

I'll update, but any other ideas?

Thanks,
Clark

[malcolm2]

Car sat for about and hour.

I started it. It idled and rev'd to 4000 smoothly. ran for about 5 minutes.

#3CHT went up to 250*F

Prior to the January issue the cruising CHT was 350. The past month it stayed between 300 and 350. Even if the gauge or sender has problems, it would not cause the sputtering.

Now to the filter.

EDIT: Filter seems OK. I hate that you can't see thru it. I poured gas thru it backwards several times, blew thru it both ways. Good flow all around, no sediment came out.

[r_towle]

sounds like it flooded, temp going down too fast, sputtering.

See if there are tests for the AFM on Ljet.
Link up top, right side, 914 info, other sites.

There is an ljet site to help you diagnose it.

Wiring may be at fault, or the AFM may be faulty.

Rich

[malcolm2]

sounds like it flooded, temp going down too fast, sputtering.

See if there are tests for the AFM on Ljet.
Link up top, right side, 914 info, other sites.

There is an ljet site to help you diagnose it.

Wiring may be at fault, or the AFM may be faulty.

Rich

I will read up. I have not heard of FI ever being flooded.

As mentioned, 1 common denominator is the speed. I rarely take her up to 80. Really it is actually 75 via a phone app. So you might have something.

[r_towle]

Djet floods when the MPS fails.

Ljet could flood when and if the flapper door gets stuck wide open (80 mph) and then you go and let off the pedal, yet the flapper is still calling for lots of fuel.

It is a 40 year old part....

Timothy may know how to test it electrically, and to test it physically, just pull off the rubber hose and gently use a finger or pencil to feel it open and close....if you feel any notchy area, you need to rebuild it.

these things are rebuilt all the time for the 944 guys, so they could not possibly last that long.

If you look online, you will find the 944 AFM rebuilders....small shops.

I would suggest you see if you can find a spare right now...and get that rebuilt.
Till then, stop doing what you did...

rich

[era vulgaris]

One thing I've noticed with my 4 channel digital CHT gauge...if a head temp starts dropping, the cylinder might not be firing. It's happened to me twice. Once when I didn't pop the plug wire on all the way on #4. That cylinder stayed around 200*, and the engine ran like crap. And more recently I had some dislodged carbon cause a bridge short on #2 plug's electrode. And again that cylinder stayed around 200* and the engine ran like crap.

Make sure you've got spark on that cylinder!

[malcolm2]

MAY HAVE FOUND IT....
Went to remove the #3 spark plug, expecting a tight fit and OOPS>>>> (IMG:style_emoticons/default/screwy.gif)

I did not have to break the torque at all. the plug was NOT TIGHT. Might explain why the CHT registered cooler than usual too. and even why it happened going up a hill. The head actually got hotter than normal and everything loosened up... ya think?

Did the same for #4 and it was plenty tight. Both plug are JET BLACK.



both are NGK BR5es and gapped at 0.7mm so that is good. Wasn't there a photo array of plugs somewhere? I found one that says the dry black soot can be from over idling.... My car does idle too high.

[SLITS]

http://www.classic-car-magazine.co.uk/arti...uide_chart.html

Soft, black, sooty deposits easily identify this plug condition. This is most often caused by an over-rich, air/fuel mixture.
Check for a sticking choke, clogged air filter, or a carburetor problem - float level high, defective needle or seat, etc.
This may also be attributed to weak ignition voltage, an inoperative preheating system (carburetor intake air), or extremely low cylinder compression.

[r_towle]

http://www.classic-car-magazine.co.uk/arti...uide_chart.html

Soft, black, sooty deposits easily identify this plug condition. This is most often caused by an over-rich, air/fuel mixture.
Check for a sticking choke, clogged air filter, or a carburetor problem - float level high, defective needle or seat, etc.
This may also be attributed to weak ignition voltage, an inoperative preheating system (carburetor intake air), or extremely low cylinder compression.

L-jet

[r_towle]

I would suggest you put it together again, new plugs.
Drive for a week, examine plugs.

First, hunt down any and all vacuum leaks at hoses and injectors.

If super rich again, unplug cold start injector.
Re-route fuel line around cold start injector
Cap injector to ensure no new vacuum leak.

Drive it again for a week, check plugs.

You will be fine without the cold start injector.
It's getting warm and I don't need one up here...colder than you.

You can find this pretty fast if you have a valid AFR that is clean and working.
Make a change, drive same route, log data on uphill loaded long runs on highways.....

[Valy]

I hope the plug was not tighten well last time.
I would fear that the plug threds are stripped in the head.

[ClayPerrine]

If you are running 40 psi on the L-Jet system, then that is probably the cause of your rich running. The L-Jet should be 28 psi at idle, and 32 psi with the vacuum line removed.

[malcolm2]

thank you gentlemen. You have given me some things to try this week.

Is there a way to adjust the fuel pressure?

[pilothyer]

thank you gentlemen. You have given me some things to try this week.

Is there a way to adjust the fuel pressure?

On L-Jet the fuel pressure regulator changes the pressure according to vacuum signal. You can't adjust it as you can with D-Jet. Possibly the regulator is bad if you are reading 40 psi fuel rail pressure.

[pilothyer]

Check to see if the fuel pressure goes up if you remove the vacuum line from the regulator. Also see what the vacuum is on the line to the regulator. If you have a vacuum pump try to apply more vacuum to the regulator and see if the rail pressure drops.

[malcolm2]

Check to see if the fuel pressure goes up if you remove the vacuum line from the regulator. Also see what the vacuum is on the line to the regulator. If you have a vacuum pump try to apply more vacuum to the regulator and see if the rail pressure drops.

Thanks Jerry. Sounds like a good idea.

[pilothyer]

You are always welcome Clark............Let me know how it goes..............Jerry

[malcolm2]

You are always welcome Clark............Let me know how it goes..............Jerry

Jerry, everything seems to be OK. I have about 35 PSI on fuel at 3000 RPM. It does go up to maybe 38 psi on fuel at 1000 RPM.

At idle when I pulled the vacuum line from the pressure regulator and fuel psi jumped to a smooth 42. With the vacuum line on the regulator the fuel pressure gauge jiggles.

Then I checked the inches of Hg on the line going to the fuel reg. I got 20 inches at 3000 RPMs and 10 inches at 1000 RPM.

Anything on there?

[pilothyer]

Ideally you should have low pressure at high vacuum (idle) and higher pressure at low vacuum (acceleration) Do you have another pressure regulator you can swap with to check values at low and high vacuum conditions ? In summary what you are looking at is low pressure at high vacuum (idle 28 psi) high pressure at max throttle (32 psi) and somewhere around 30 psi at cruising.

[malcolm2]

Ideally you should have low pressure at high vacuum (idle) and higher pressure at low vacuum (acceleration) Do you have another pressure regulator you can swap with to check values at low and high vacuum conditions ? In summary what you are looking at is low pressure at high vacuum (idle 28 psi) high pressure at max throttle (32 psi) and somewhere around 30 psi at cruising.

I do not have one. I'll check the web. Maybe I can find something not too expensive. I bet they are not available new, are they?

Is my vacuum backwards? I had 10" at idle and 20" at 3000 rpm which seems right to me... the air is being sucked into the engine faster when it is high RPM.