hln111

I've done the wot thing. I've done the turn on, off, on to pressurize, but I've got 43lb's at the rail so I dont think it's a lack of fuel at the injectors. Again I believe it's the injectors not releasing the fuel. I recently read a thread of a person who seemed to have a similar problem and he replaced the ecm and for the last two months hasn't had any problems. Of course that's one guy's situation and possibly not mine. From what I'm hearing the distrubutor and the ecm work in conjuction to open the injectors. Is that right? If so it could be either one that's causing the no start.

aklim

If you are cleaning and testing them, why not clean and test all and not just one or two? How would you test injectors without having them flow tested? The ohm test only tells you the rough condition of the solenoid not whether a nozzle is clogged or not. Assuming he has good spark at the right time, it does point to a fuel issue. Since he is getting fuel, as evidenced by it running after the starting fluid, I tend to think it isn't spraying just right.

aklim

Easier to pressurize it at nighyt and see if the plugs are wet in the am. Besides, the injectors are old and probably dirty so why not have them thoroughly checked? I have seen injectors after a few years build up crud.

aklim

Doesn't hurt anything but what would the point of that exercise be? If you really suspected low fuel pressure, the simple way to check it would be a gauge.

joe paco

i'll let someone else chime in. the dist and ecm fire injectors, correct. your issue is time related more than temp, unless you are in cold weather now. the prime was in case you had not verifed the fuel rail pressure right before starting.

joe

aklim

43 is decent pressure. When you say it got 43, you mean that if you turn it on, you get 43 and it can hold it for a bit, right? It doesn't drop off quickly, does it? (Assuming you have a stock FPR, that is)

Try cranking it and hooking up an idiot light to one of the injectors and see if it is pulsing if you really want to nail that one down

joe paco

explain in one sentence why the starter fluid helps. I gather that you are selling injectors? tell him how to start the engine, pls.

aklim

Poor atomization of fuel, IMO.

Yep. I sell injectors. I can sell you a set with a 10% markup from Jegs or Summit.

3 things are needed. Air (I assume he has enough), spark (seems to be running ok except for a hard start) and fuel (has enough pressure and runs well except with a cold start.

When the cylinder temp is higher (after running or being started with starter fluid), it vaporizes the fuel more efficiently than when cold. If your injectors are crudded up, they will stream the fuel as opposed to mist it. Hot engine helps it mist better which is why, after starting, it keeps running ok. Cold engine and it is harder to start with the fuel droplets being bigger.

All in all, is there any harm to cleaning the injectors? You will have to have them cleaned and checked sooner or later, why not now when there is suspicion?

aklim

BTW, after this gets fixed a new O2 sensor and plugs won't be a bad idea. No telling what is left on the sensor after the fluid gets burned and passes over it.

And yes, I also sell O2 sensors and spark plugs. Not to mention muffler bearings and blinker fluid

hooked073

You said does not start?? Do you mean long crank and then start? or do you have to use starting fluid everytime you need to start it?

hln111

It seems to be becoming worse. Now when it sets for 4-5 hr's I have to use fluid to start it. You can crank till the cows come home and it wont start, but one little tiny shot of starter fluid and starts right up. I'm really leaning towards the ecm.

hln111

hooked073

Chaces are it is not going to be ECM. by adding starting fluid you are not changing anything the ECM would see to make it run so I would rule that out. The only thing you are changing is what is going on in the combustion process. First thing I would check to see is what the ECM is seeing as far as temp in relation to the real temp. In reality with out getting to deep, to start all the ECM realy looks at is temp and throdel position. If your temp is correct and your TP is correct and assuming you do have fuel pressure I would look hard at the injectors. It is not hard to rule things out scan the thing when it will not start see what you have..

aklim

Good point. Where is the temp sensor at again on a stock intake? Probably right under the throttle body, IIRC. I haven't had a stock intake for a long time so IDK. I suppose it might be cheap enough to simply replace if he doesn't have access to a scanner although I really don't like that sort of wrenching.

hooked073

It is located right below the thermostat housing.

aklim

Good to know. Sometimes the aftermarket moves things around so much you have to rewire things. I felt my IAC was too tight and had to rewire it. In fact, my AC compressor kept shorting out the fuse because the wire was too tight till I had rewired it to make it better.

hln111

Here is a thread I found on our site. I realize it's not the same year, but close.
"I have a
1992 LT1 that had a very random start problem. Fuel Pressure was Ok, Spark
to plugs was fine, no error codes were set in ECM. Once the car started it
ran fine. Finally took a #47 (12Volt) bulb and put it across the fuel
injector wires. Found that when the car was dead the lamp never lit at any
cylinder. But when it started I could see the ECM lighting the lamp. I
checked the grounds to the ECM all were fine. Finally ordered another ECM
from The Last Detail. Has been starting fine every time for the last 2
months. (Just a side note the problem got progressively worse from the
point the failure first occured.) Hope this help anyone with a similar
problem!"

hln111

hln111

Just another bit of information. I've noticed that in the morning when going to work ( after the car has sat all night, temp around 50-55 degrees) the car usually always starts. But when I leave work after 8 -9 hr's (temp near 80) it won't start. Maybe it is temperture related.
Yesterday after returning home (temp 80) the car sat for about 4 hr's then wouldn't start.

hln111

joe paco

I thought it was time, also, since temp is summer in the US.

tech bulletin I have says to unplug TPS so that ecm sets a nominal value for starting -firing- injectors. that should give you a clue at least, if that applies to 91. Bulletin was written in 85.

don't recall if you said it starts 10 times to 1 after first starting, or whatever. you start it more than 2 times a day. right?

hln111

Yes I start the car several times a day after I leave work but it's notstarted at all while I m working 8-9hr's. After it's started once you can start it as many times as you like without a problem as long as you don't let it set for several hr's at a time. When it's started, at any time, it doesn't react as a flooded eng. would and there's no smoke. It seems a lean condition to me, but I could be wrong and very likely am.

hln111

joe paco

my 91 starts and runs 'almost normal' cold with #1 and #8 injectors unplugged, just to test the theory.

also starts fine with throttle position sensor TPS unplugged -a test for in case the ecm sees a high voltage value at TPS and "restricts pulse time to injectors." clear flood time. if unplugged ecm uses default voltage input.

distr sends reference pulses from purple/white ckt 430 when engine is turning, no idea why it sees pulses with starter fluid injected. agree that the ecm is not pulsing injectors, any of them.

maybe you said -have you checked for ecm dtc codes?

how are you accessing the TB to spray fuel in?

does in ever "fire" one cylinder even once, to show it has spark and some fuel?

sympathies, joe