3.2 . I have good spark and I have good fuel injection, but no start

[marlinaness]

I have gone through the Bentley and all the individual parts on the 3.2 are in spec. I have good spark and timing with all cylinders. I have fuel injectors injecting gas. So, gas and electrics are there (maybe not synchronized like they should be).

The most I can get is an occasional small backfire out the muffler. I have gone through all the docs I could find on the website and have not found symptoms like this. Anybody know of anything on the top side (like a connector or vacuum leak or plugged orifice) that I might have missed before I go back to check things like the cams and all that? What is surprising me (and I am a novice) is that the vane on the intake stays closed when cranking. I would think it would open somewhat to let some air in. Helping it move does nothing either.

Time to go study the books some more.

thanks in advance for any reocmmendations
Marlin

[Bob Kontak]

Originally Posted by marlinaness

What is surprising me (and I am a novice) is that the vane on the intake stays closed when cranking.

I know little about 3.2s/DME. I have an SC. But while we wait for someone who knows something.......

Is the vane the throttle plate? That is opened mechanically by your foot, right? On the SC, there is an air sensor before the throttle plate that determines how much air is coming in. As it is moved by the incoming air created by the starter engagement it pisses fuel into the cylinders and all of the cold-start throttle by-pass air valves allow air to get into the combustion chamber to start. There is no throttle plate movement on start up.

On your car, the flapper thingie (air flow sensor barn door) moves to tell the ECU that it is time to squirt fuel. Not the throttle plate opening.

Folks talk a lot about the DME relay causing problems.

Try going into "Search" then "Advanced Search" and enter "DME Relay" or "Carrera will turn but not start" and do some reading.

FIY and with no value at all - The early Motronic systems as in your car sprayed fuel one bank at a time. The three left cylinders / three right cylinders. They had an on/off spray function the SC did not have. That is why the Continuous Injection System has it's name. It sprays all the time.

I spent many nights in the Herrington Inn in Geneva. Nice place.

All the best.

[Targa Me]

try replacing the dme relay with a known good one.

[Tippy]

Not sure how much the AFM opens during starting but indeed opens a lot during idle. Maybe 1/4 the way of full travel?

[Quicksilver]

Originally Posted by Bob Kontak

. . .
FIY and with no value at all - The early Motronic systems as in your car sprayed fuel one bank at a time. The three left cylinders / three right cylinders. They had an on/off spray function the SC did not have. That is why the Continuous Injection System has it's name. It sprays all the time.
. . .

The 3.2 DME fires all 6 injectors at once. The reason it has 2 circuits is that there are 2 driver circuits in the DME.

----
You haven't said how you know that you have spark and fuel pressure. How you test that would add a lot to the troubleshooting process.

A cheap oscilloscope off of Craigslist will help you a long way down the road with finding out what is wrong. You can easily test the crank sensors and the injector pulses with that.


If there is someone near by with a3.2 car you can try your DME in their car. If it doesn't run it is the DME. If it does then you have sensor or wiring issues.
BTW - It isn't 100% safe to test by putting a known good DME in a car that has issues. For example, if the idle control valve is shorted it can burn up the DME.

[theiceman]

if when cranking you have spark and also have injectors firing in fuel then the dme is working. that air intake flap not opening is a clue. i wojld be checking compression too.

[T77911S]

cold start valve working? (if it has one). if not, could temp sensor be bad telling the DME the engine is hot when it is not? just a thought.

fuel pressure?
how do you know the injectors are firing?

do you have a good quality spark? how are the plugs? you might just replace them in case you have fouled them.

[john walker's workshop]

air, fuel and ignition. should run, so you don't have one of them. did you do anything else, like mix up the wires on the cap?

[theiceman]

Originally Posted by john walker's workshop

air, fuel and ignition. should run, so you don't have one of them. did you do anything else, like mix up the wires on the cap?

.... if all the above is present I would be checking compresion.... no compresion no start ... lower on the list of probabilities but is up next ..

oh and as far as the CHT sensor is concerened that is a possibilty .. just unplug it .. thei simulates a cold engine so should richen the mixture. I think its the lower of the 3 white connectors ont he left side of the engine.

I do have one question though ... all this cranking with no fire the car and garage should be reeking of gas by now .. if it doesnt i would be wonderin.....

[Chuck.H]

Are you sure it isn't flooded? Try to start it while holding the accelerator to the floor... A faulty head temp or AFM sensor could cause a very rich condition, too rich to start.

Chuck.H
'89 TurboLookTarga, 336k miles

[Tippy]

Need a fuel pressure gauge to see if fuel system is maintaining pressure.

[kidrock]

as long as we're all throwing out WAG's, pull the white connector where all your sensor plugs are located (left side of engine, intake #2). That white connector is your Cylinder Head Temp Sensor.

Grab a paperclip, bend it into a "U", and jumper the 2 female connectors....see if your engine starts. It's a 2-minute stab in the dark.

[marlinaness]

I have been travelling to NY, still not back yet, but greatly appreciate all the comments. I will try every one of these this weekend unless we have concurrence that my conclusions are correct.

For further clarification:
spark plugs are new. It is on engine test stand.
I tested the spark by connecting sparkplug to every wire and observing the spark. I also put timing light on each wire and saw the timing on the timing pulley. Therefore I considered the spark good.

I removed the fuel rails on each side and observed fuel being discharged roughly equally on cardboard paper on each side. I could hear the injectors with a stethoscope. So, I considered the injection good, fuel pump definitely pumping, and pressure was good (although I will probably verify the exact pressures).

based on those two I think the DME and relay are fine. I had a spare DME and have the same results as above.

I had did check the reference and signal sensors and verified I had the correct connections, although one could be bad, I am at least getting the spark and timing right so I verified one is good. Maybe the counting sensor is bad, but the other is good. I think I read the counting one is used for starting only. Measurements on each were good. Did not verify with oscilloscope.

Based on the feedback my plan is to:
1) check compression
2) find out why the AFM is not opening so air can come in
3) check CHT

then I will be lost again
many thanks all for your patience
Marlin

[kodioneill]

Plugged catalyst?

[benzboy]

heres something to check. i was having problems with my 85 3.2 of stalling when i pushed the clutch in and came down to idle. my breather hose for the engine to he top of the oil tank was cracked. i haven t replaced it yet, but i took of the hose, and all the car will do is crank over like it wants to start. so im assuming i fixed my problem. not hard to get to. might scratch your arms a little bit.

[kodioneill]

What do you mean "the engines on a test stand" ?

[marlinaness]

The engine is on a test stand with all oil hoses hooked up, battery power provided, key starter, fuel tank, etc. It has a test pipe with muffler. Not catalytic converter. The intake is reversed to go into a 914. I will post pics when I get back. I had traded a motorcycle for the motor. It had three pulled head studs, which I replaced with steel. I pulled a chevy 350 out of the 914 Eagle GT. Had a 915 rebuilt with flipped ring and pinion and I will put all this in my 914 Eagle GT as soon as I prove the engine.

air or vacuum is one of my top things to look at as I haven't been able to find exactly how all the mini hoses go.

Thanks. Marlin

[SalDoyley]

try replacing the dme relay with a known good one.

[marlinaness]

compression was there. I figured it was synchronization of fuel and timing.
looked at the valves with respect to TDC. intake opened right after TDC.
didn't make sense.

turned distributor 180 degrees

engine started. now solving for crappy idle. time to fix the vacuum lines.

many thanks to all. I felt like Dr House without knowing very much and had the greatest set of diagnosticians around to help solve the problems.

regards
Marlin