Symptoms and Diagnosis

[MidLifeCrisis]

I'm posting this in the Spider forum because my 74 GTV is equipped with an '85 L-Jet engine.

Symptoms/observations:

1. The car is difficult to start in the morning. It used to fire up within a second or two, but now I have to crank it several times for extended periods (10 seconds) with breaks in between before it catches. I'm not touching the accelerator, and can smell gas while I'm cranking it. The rest of the day it starts right up, but the time it does take to start seems directly proportional to the amount of time that it sits between starts.

2. When the car has warmed up, it will occasionally sputter at low rpms when I'm starting from a dead stop. It seems to have good power and smooth acceleration otherwise.

3. I cleaned the plugs thinking these might be fouled. The electrodes and ground were covered with white powdery stuff.

4. I placed a timing light on the car and while the "F" mark jumped slightly from one side to the other of the pointer, it looked like it averaged on center.

5. It idles well with an occasional "skip". I put a dwell tach on it and it says it's idling at around 980 rpm.

I have a newly acquired exhaust leak in the forward muffler that is pretty significant and have a replacement on the way from Centerline. Could the exhaust leak be contributing to the symptoms I've described?

Any feedback is appreciated.

Thanks,

Michael.

I have an exhaust leak in the forward muffler

[ghnl]

Most problems with the L-jet Spider are false air leaks or iffy grounds. All air entering the engine must pass through the AFM (Air Flow Meter). Any intake leaks between the AFM & the engine ('false air') means the AFM sends erroneous signals to the computer. GIGO - Garbage In Garbage Out.

Difficulty with cold starts could either be the CTS (Coolant Temp Sensor) or the TTS (Thermo Time Switch) or both. Also the AAV (Aux Air Valve can be problematic. If it doesn't open fully when cold or close when warm it'll mess up either cold starts or warm running (or both...).

Here's a useful link for info about L-jetronic Spider diagnosis.

[MidLifeCrisis]

Thanks ghnl,

I glanced at the referenced article before, but read it thoroughly today. I guess there's no silver bullet when so many different things could cause these symptoms. I think I'll start with the AAV since this seems easy.

Michael.

[ghnl]

Yeah, the L-jet is really a system - all the components have to be working correctly.

The quickest/best way to test the AAV is the freezer/oven test. Remove it from the car. Put it in the freezer for 20 minutes then look through it to see if the passage is fully open (or nearly so). Then put it in an oven at 150F for 20 minutes and check that it is fully closed (or very nearly so).

If it fails the above test, try spraying some carb cleaner into it, sloshing it about then washing it out with soapy water and rinse & dry.

If it now passes the cold/heat test re-install it and drive your car to the Lotto agent to buy a ticket - today is your lucky day!

[asg007]

Different car, similar issue. My 164 had a similar problem, turned out to be a bad coil-distributor lead, but I chased it for some time.

good luck

[carsdlt]

Another thing to check is your battery voltage. If it's weak - will crank the engine OK, but not enough juice to trigger the EMC - prolonged cranking upon cold start-up is not un-common. IIRC, you need about 11.5 while cranking. Oh, and don't forget to check those grounds!

[Tifosi]

If you've got the whole of an L-jet system in there, it'll also have the ignition ICU.

The fat white wire on the coil connects to that, and might be worth checking, unless you've got a stand alone ignition from RML/Centerline/Crane/etc, in which case that wire should be disconnected if it's present at all.

[MidLifeCrisis]

Quote:

Originally Posted by Tifosi If you've got the whole of an L-jet system in there, it'll also have the ignition ICU.

[MidLifeCrisis]

I've gone through the L-Jet troubleshooting guide (thanks), and think that I've isolated the problem. My Cold Start Injector is not doing anything when the engine is cranked.

My question is, do I need to replace it or is there a fuse somewhere in this circuit that I should check? I cleaned all the contacts to include the ones that go to the relay on the firewall... still nothing.

Any suggestions?

[ghnl]

TTS (Thermo Time Switch) checks OK? See the replies by PapaJam in this thread for the correct info about CSI operation.

(I need to edit the info about the CSI on the L-jet diagnosis page)

[Elio Comello]

Hi Midlife,
One thing that is easy to check but not well covered in above threads and refferences is the Manifold Atmospheric Pressure Sensor. It sits next to the Engine ECU, behind the pass seat on the sidewall. It is like a silver mushroom.

In the L-Jet the distributor has no centrifugal or vacuum advance. The ignition timing is set be the ECU (silver one), which is fed the signal from the MAP sensor (Bosch).

This sensor is known to fatigue and leak, usually announced by high pitched whistle that varies in pitch with load and time. The furthermost connection on the intake manifold is piped back to this sensor. Remove the vacuum line and give a gentle suck (gentle now) and is you draw air, that will confirm you have a problem there.

This may also explain the variation in the timing you are seeing with your light.

The Cold start injector only operated as governed by the Thermo Time Switch. At start up you should be able to see it spray startup fuel (it is easy to remove). After the thermo time, it will not spray, so caution on your diagnosis.

Best regards, Elio

[espresso veloce]

A failed MAP sensor can cause a variation in idle timing? Shoot. I drove my L-Jet spider with the MAP sensor hose disconnected (to stop the whistling) and the throttle position switch unplugged for the better part of last summer without any noticeable performance issues. Granted, my mileage was not as good as it could have been, but I think it only made a difference overall of a couple mpg when cruising across the state.

Tim

[Tifosi]

Quote:

Originally Posted by espresso veloce I drove my L-Jet spider with the MAP sensor hose disconnected (to stop the whistling) and the throttle position switch unplugged for the better part of last summer without any noticeable performance issues.

[Elio Comello]

If you have the MAP connected it will affect spark advance as seen by the timing light.
When you disconnect the hose to the MAP the signal to the ECU does not change. If you leave the MAP with the leak connected, the deflection in the bellows will exacerbate or lessen the leak, causing the MAP signal to change, causing the ECU to vary the timing. This is governed by the feedback time lag and the type/size of the leak.

Best regards, Elio

[MidLifeCrisis]

Quote:

Originally Posted by ghnl TTS (Thermo Time Switch) checks OK? See the replies by PapaJam in this thread for the correct info about CSI operation. (I need to edit the info about the CSI on the L-jet diagnosis page)