flooding/no start intermittent

my MJ, 89, 4.0 renix.
The intermittent starting problem persists.

have spark, seemingly at the correct time, have fuel.
actually too much fuel...... according to the new spark plugs
i posted some info in the past on another board. and have changed.....

dist cap, rotor
cps
plug wires
plugs autolite platnium replacing bosch platimum
fuel pump
injectors (19lb accel replacements), thought the originals were sticking open
oil and filter (after smelling fuel in oil)
coil and module have about 70k on them

When it does start, it runs fine... with no issues

So here I am again.....
Would not fire yesterday afternoon, but did this morning, but it shows the same signs of rich condition...

got it inside shop, it loaded up and stalled just as I entered shop, pulled #3&4 plugs (easy to get at), soaked with fuel

tried an 'old' coil and module...(oem with 70k) made no difference...
and when i test the spark, i can see no 'issue'

What controls the injector pulse? What could cause the flooding? Do the injectors fire sequentially?

have in the past checked resistance on the cps, seems in spec

what next??

then I posted again.....

Bumfuzzled...

performed some tests on components... cold engine, before attempting a start
this is after a no start condition, leaving it overnight

MAP sensor, voltage checked fine, output voltage will change when applying vacuum to port.. will hold vacuum

intake air sensor and coolant temperature sensor check fine for temperature range vs ohm reading per chart.

i did find the output voltage from the TPS to be low, .38 volts instead of .8 volts, I was able to adjust to .8 volts and have 4.8 volts at WOT. I performed a sweep test and could not detect any problems (no analog meter)

The CPS checked 200 ohms

The coil I have checks in spec on the primary +/- terminals (4-6 ohms) and from the secondary to either of the primary i have 4650 ohms another newer coil checked 6500 ohms

checked the ground strap visually, it seems to have no issues and is tight

i was not able to backprobe the stator to check it

for kicks after the above, i attempted a start......

the damn thing ran...
i ran it for about 6-8 minutes, still smelled a bit rich, and then shut it down.

after about 15 minutes, i tried to re-start......

nope.

same ole crap, smells flooded and 'almost' runs but will not 'catch'

pulled #3 plug, seemed gas soaked

grounded plug and checked for spark.... had what should be ample spark


what next??

change your cps 90% of the time thats it

I have read somewhere in this forum details of how to test the CPS while the engine is cranked to see if it is producing a high enough voltage. Had something to do with spacing, proximity to the flywheel and age of the CPS. You might search for that procedure and see if there is a gap problem on the CPS mounting.

On the flooding problem, In my short experience a no start condition can flood the engine (to the point where it will not start) in something like 60 seconds or less of cranking. So your real problem may not be flooding, it just may be that flooding is making it difficult to isolate and identify the real gremlin(s). I think I read somewhere in this forum that holding the throtle wide open while cranking will help the engine breath enough to unflood it.

Also:

Test or replace the fuel pressure regulator. It is vacuum operated and it reduces the fuel pressure at the injectors from the pump at idle.

A bad O2 sensor or bad connections at the O2 sensor will make it run rich.

Do you get at least a 1/4" hot spark gap?

The distributor, wiring harness and the ECM (Electronic Control Module) itself sound like the last 3 items to start testing.

Thanks for the response......

yes, understand cps should make a small voltage... .8v AC?
will try that, even though it is basically new (less than 300 miles) and it checks 200 ohms resistance.

i did read somewhere of a 'flood clear' by holding throttle down, ECM will shut down injectors....

When I am trying to start, it is one of the things i do that seems to make a bit of difference, it tries to run....

I will test FPR again.... previous trials showed it to be working, and no fuel in the vacuum side of it..... won't hurt to hook up gauge again.

I thought the O2 sensor only affected mixture during closed loop mode... and engine is in open loop until started, and warmed up??

I grounded body of spark plug... it arcs across gap, looks yellow-blue...

i will find a way to back probe stator in the distributor....

any real 'tests' for the ECM?

and again..... thanks for response!

Has the fuel pump ballast resistor been OK'd yet?

Yes,
checked 1.1k ohms, which is molded on the ceramic ...

thall said:

Thanks for the response......

yes, understand cps should make a small voltage... .8v AC?
will try that, even though it is basically new (less than 300 miles) and it checks 200 ohms resistance.

i did read somewhere of a 'flood clear' by holding throttle down, ECM will shut down injectors....

When I am trying to start, it is one of the things i do that seems to make a bit of difference, it tries to run....

I will test FPR again.... previous trials showed it to be working, and no fuel in the vacuum side of it..... won't hurt to hook up gauge again.

I thought the O2 sensor only affected mixture during closed loop mode... and engine is in open loop until started, and warmed up??

I grounded body of spark plug... it arcs across gap, looks yellow-blue...

i will find a way to back probe stator in the distributor....

any real 'tests' for the ECM?

and again..... thanks for response!

Click to expand...

You're right about the O2 sensor, I think I was trying to point out that the early start and run control is open loop rich fuel/air mixture to start with and that it stays that way until the O2 sensor is working (hot) and ECU switches to closed loop mode. Thus the smell of unburned excess gas in the exhaust?

No real ECM tests I know of yet, except to swap it with a known good one. Have your tried removing it, cleaning all the electrical contacts on it and the wiring harness connector at least, and looking for burned or bad spots in the connections/wire?

Have you checked to make sure the distributor timing is exactly correct? I know you said it was running, but as I recall mine ran for months (poorly but it actuall drove) with the basic distributor timing off by one gear tooth. Set it to TDC using the timing marks on the harmonic balancer and see if the rotor is pointing directly at the # 1 plug.

"i did find the output voltage from the TPS to be low, .38 volts instead of .8 volts, I was able to adjust to .8 volts and have 4.8 volts at WOT. I performed a sweep test and could not detect any problems (no analog meter)"

Could this have been an indication of a problem with the throttle body itself? Perhaps it is not getting enough air at the start / idle throttle position????? The ear on the stop, and the screw at the stop could be off if someone else improperly fixed a prior TPS problem by bending or adjusting them? If so it might not be getting enough air at start up, and thus be flodding it???? I believe there is an a factory idle air screw hidden on the side of the throttle body too, underneath of a plug.

You might try out a junk yard throttle body to see!

thanks again for the replies... comments are appreciated!

this is a two owner (me and one other) 150k MJ

I will proceed with some various testing this weekend when I have more time...

i will remove the ecm and check connections.

the distributor has not been removed from the block. but I will look at it for possible timing chain problems... but i have had no other symptoms of timing (backfires, pops, etc)... and when it does run, could not ask for it to run any better.....

the idle stop screw has not been 'adjusted', nor any modifications to factory linkage.

I had installed the TPS some time ago and bent no tabs... that is why I was surprised to see the voltage reading 'off'...

you do bring up a good point though...

I will check the idle bypass passage for blockage... I know of no one around that has a testing device for the Idle air control motor (the excercisor)...

just trying not to throw money at it, but get diagnostics down to detect what is wrong...


.

Re: flooding/no start intermittent (update)

continued with diaganostics...

double checked sensors and their outputs

the CPS still checked correct ohm value, so I checked the output voltage... 'almost' .5 volt .48 volt..everything says it should read higher, so I obtained another CPS, installed.... checked it also for output....... VERY Little difference.. .56 volt... grrrrrrrrrrrrrr

removed and checked relays

I have had a fuel pressure gauge attached, so I was certain of pressure and leakdown was acceptable , not immediate

was able to back probe stator in distributor, it was 'cycling' when turning over, passing test in manual.

confirmed timing in a rudeamentry fashion, removed #3 plug (accessable), then connected and grounded plug and turned er over... on compression stroke (finger check) plug would fire at correct time.

i also removed the autolite platinum plugs and installed new champion stock plugs....

still no start......

this sorta did it for me... :smsoap:


I removed the lower dash knee panel to access the Computer....

removed it..... could see nothing with connections... actually they were difficult to disconnect....

Obtained a refurbished computer from AZone.

Installed.....

Still no go when I tried it, not moving anything..:tear:

checked for spark... seemed fine....

Tried one more time, but pressed accelerator..... and released...

it fired!
Ran... Idled... revved.......
let it idle... but it is extremly rich... even after warming up a bit.

tested the MAP voltage..... about 1.9 volt to 2.2 volts at idle... according to sources, this voltage is 'ok'.

removed the vacuum from MAP..... immediately died!
restarted though..

Shut it down and left it for a few hours to bone up on WHY RICH?

Went back to it......

Double checked the TPS adjustment...
Using the % method it is right on adjustment.... 3.8 volt is the 83% of signal volt

Started it up again......so far so good, just RICH...

I also cleaned the Idle Bypass .... was not that bad, no blockage of passages

I need to change the oil AGAIN... smells like gas.. before driving it, so I will get an O2 sensor and probably a CTS to change while in the air.. (even though the CTS checked fine on ohm reading...

Did the Computer 'fix' it......... damnedifIkno.........

.

I have read somewhere in this group about adding flat washers behind the CPS sensor to get it closer to the flywheel teeth thus getting a higher signal strength, more volatge out of the CPS signal generator (sensor). You might look into that further with a search here.

Here are 2 excellent detailed sites on how to diagnose all sorts of engine problems with just a vacuum gauge. They are well worth the time and effort, easy to do, inexpensive and they can elliminate a lot of guess work.

http://www.ncf.ca/~ag384/vacuum.txt

http://www.obd-codes.com/howto/diagnoseengine.php

Check the resistance, ground, between the firewall and the battery negative post, and then check the ground resistance between the valve cover (or engine block) and the negative battery post. Both should be less than 1 ohm! If not clean the connectors and the surfaces with scotch brite to bare metal and reattach and retest.

Have you tried putting the original injectors back in? Could the new Accel injectors be too rich?

Also have you checked the distributor for side to side play in the shaft? It may be at its wear limits and thus affecting the timing a bit. 150,000 miles! If it is just a bit out of tolerance it can affect timing, starting, fuel burning efficiency (rich/lean?) and cause a slightly low idle vacuum from what the link sites above say.

Thanks for the reply again.
I have had the opportunity to drive it a few times since my last post. It has started each time flawlessly... and runs smooth as silk... idles as it should, etc

I just returned about 30 min ago from about a 20 mile ride, with one stop turning it off and it sat for about 30 min. It fired right up.

I did previously remove the grounds and clean, but did not ohm them out. All wires were intact.

No, not placed old injectors back in. The Accel were 19lb/hr which should be same as stock, but with improved pintle and orifice. Fuel pressure is 'book' and regulator is working.

If it runs as it is running now, I have no problem. I think it is a 'lil tired... and it may be complaining about not having as many miles put on it as it used to...

Future...
See if I get starts each time, see how it runs..... replace fuel tank, rear main seal... do my regular maintenance, drive er till she quits and then investigate a stroker.