new problem

moosemeadows · Jun 17, 2016

I'm at a loss again. Here's what I'm dealing with. 93 4.0 in a 87 Bronco ll. Vehicle sat for a couple years before I got it. Today was on my way down to DMV for title change stopped for some fuel ran in to pay went to start it up and it just spun over. Pushed it out of the way to the curb and let it sit for a few as it's had this issue before but usually starts right up but runs rough like it was flooded. Today no luck so I sat thinking "It'll start" but not this time. Started doing some checking had some fuel pulled a couple plugs and they were soaked. Called a neighbor who came to get me so I could get it towed home. By the time we got it back about an hour had elapsed from finding it was flooded. Jumped in and tried to start and it did. Ran just like a flooded carbed car does. Started doing a little more looking and testing after it cleaned itself up. Checked fuel pressure with only key on was at 10# then started it up and she went to 39#. Let it run till temp came up and shut it down. Still at 39# for about 10 minutes then started to drop. Dropped 10# in 30 min and still dropping. My guess is that I've got some injectors that aren't shutting off or sealing. When it was running pulled vac line off at FPR to see if that was blowing fuel out but nothing came out and line was dry.So far I've replaced in tank pump and frame rail pump fuel filter in line resivour without filter as the one that came off was. I can't figure any other way that fuel would get to plugs other than injectors especially if FPR isn't blown.
I'm at the point now of pulling it apart and send the injectors to be tested and patterned. Not a big job but any other other ideas from you all before I do?
Another thing it's been doing is that the idle in the am is normal about 800-1000 but when I get to work about 40 miles later it's up to 1500-2000. I've replace the temp sender for gauge single wire and ETC 2 wire for computer and factory 195* thermostat.
Mileage hasn't been great either about 17-19 but I can live with that. It's alot better than 6-9 my 72 Chev gets.
Looking to hear what you all have to say and think.

RonD · Jun 18, 2016

Yes, certainly reads like leaking injector.

Couple of tests to do.
Hook up fuel pressure gauge
Start engine
Shut engine off, pressure at 35psi
Turn on the key
See if pressure drops faster
You are testing to see if one of the two fuel injector Computer controlled Ground wires is shorted to Ground.

1993 4.0l computer should be Batch fire injection
When key is turned on all 6 injectors get 12volts, but are not grounded so stay closed.

Computer uses two Ground wires each hooked to 3 injectors in a Batch fire setup, sequential injections would use 6 Ground wires.

If one of these ground wires had rubbed thru and was being grounded........then 3 injectors would be opening and pressure would drop fairly fast.

Also after turning key on, engine off, move wiring harness around while watching fuel pressure gauge, you said problem was intermittent, so..........could have intermittent ground short

Next test would be the Clear Flooded engine test.
If TPS can detect Wide Open Throttle(WOT) then engine should not start if gas pedal is pushed to the floor.
Key on
Gas pedal to the floor and held down all the way
Crank engine
It should not start or even fire.

Clear Flooded Engine is a routine in the computer, to do just what it says.
If key is on, engine is at 0rpms, and TPS is sending above 4.5volts(WOT) to computer, then Computer starts Clear Flooded Engine routine.
Computer won't ground any of the injectors, but spark will still be working.

So in Clear Flooded engine mode engine will not start because there is no fuel coming in.

If you release the gas pedal or engine fires enough to get to 400rpm computer will exit Clear Flooded engine mode.

Assuming TPS is sending above 4.5 volts to computer when gas pedal is to the floor.
And engine fires or starts then gas is leaking in, and you can use that to id which injector(s) may be leaking.

Disable spark, unplug the coil pack
Cycle key on and off a few times to build up fuel pressure.
Press gas pedal to the floor to start Clear Flooded Engine mode
Crank engine a few times, it won't start this time because no spark.

Now pull out each spark plug and see which ones are wet

moosemeadows · Jun 18, 2016

RonD thanks again for your thoughts.Been busy today but after breakfast tomorrow I'll go give your tests a go. Will give you a report on what shakes out tomorrow.

swynx · Jun 19, 2016

might also check the fuel pressure regulator, pull the line off of it, and smell it for fuel.

moosemeadows · Jun 19, 2016

swynx thanks for that thought and that was one of the first things I did and there was nothing there. Any other thoughts? Happy Dad's day all and enjoy!!!!!!!

moosemeadows · Jun 19, 2016

RonD here's the results. Fuel pressure while running 38# when shut off 38# after ten minutes drop to 35# Didn't make any difference when wiring moved about Did notice a fuel smell on left side while moving wires checked fuel connections all tight and no leaks or residue of any. On the clean flooded motor test between the gry/red & gry/white got 0.04 with digital meter set to 20 scale Tried analog meter and didn't move the meter at all. When pedal released eng cranks and starts normal when cold Didn't try hot start though. So is my TPS bad then or is it a wiring issue to it?

RonD · Jun 19, 2016

So engine did not fire or start when cranking engine with gas pedal to the floor?

And fuel pressure didn't drop during the above or with key on.

Not sure what ohms you were testing?

You test TPS with volt meter set to DC volts
Ground meter to engine, or battery negative
Use a sewing pin to pierce center wire on TPS to test it's voltage while connected
Turn on the key
Center wire should have .69-.99 volts, under 1 volt, throttle closed
Open throttle manually, voltage should increase steadily no jumping or dropping, at WOT voltage should be above 4.5volts
Also after testing use gas pedal to set WOT, push it all the way to the floor and put something on it or use a stick against the seat to hold it down all the way, then make sure TPS voltage is above 4.5 and throttle is actually wide open.
Throttle cables can stretch so you no longer get WOT with gas pedal down all the way.

Google: Ranger throttle cable mod

If thats the case

moosemeadows · Jun 19, 2016

RonD engine cranked no start with pedal mashed fuel pressure no fluctuation Got .3v on center wire throttle closed no voltage as throttle moved to open. Going to get another DVM with the proper leads rather than messing with pins Can't do a very good job with those I'll let ya know what happens next Thanks for the insight

RonD · Jun 19, 2016

Not a leaky injector then

moosemeadows · Jun 25, 2016

Here's some further findings 1) when warm the idle is 1200-1500 stone cold starts it idles @ 8-900 then as warms idle raises 2) TPS has 4.9 v at grey white wire where it should only have less than 1v KOEO as throttle is moved from idle to WOT goes to 5.0 v up and down smooth also checking the ground at TPS it only has 7.5 v where it should have 10-12 v maybe wiring issue 3) no codes from ECM not even 11 code saying everythings ok 4) with pedal floored engine will start maybe bad injector 5) with pedal released engine starts and runs for 10-15 secs then shuts off acts like fuel starvation but if pedal feathered it will run but idles at 12-1500 again

AllanD · Jul 13, 2016

Yes indeed, a 1993 4.0 is "Batch Fire" but the 1993 engines were built with the anticipation of a switch to Sequential, so the engines were all built with the same injectors as the 1994 SEFI engines.

Which is to say the faster acting "Disc Pintle" injectors, these from experience are more prone to sticking due to "varnish" is an engine is allowed to sit for months or years.

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