Help troubleshooting TBI, please (long post)

[budojeepr]

Hi all,

I need some help troubleshooting the TBI-injected 454 in my J-4000.

Last summer I parked it next to the house while I worked on my diesel Wagoneer; it was running, albeit a bit roughly, when I parked it.

Now that I'm dd-ing the Wag, it's time to freshen the J-truck up. Now it won't start, and it's obvious why: the injectors aren't spraying gas.

Here's what I've done so far, in order:

1. Siphoned all the gas out of the fuel cell.
2. Changed the fuel filter.
3. Purged the fuel lines by running the fuel pump, from a clean container of new gas into another container. The TBI return system just dumps it back into the container after a round trip. Refilled the fuel cell with 5 gallons of nice new clean gas.
4. Changed the engine oil and filter.
5. Removed the TBI unit, disassembled, and cleaned it. Note: Since I don't know Jack about them, I did not do anything with the injectors.
6. Reassembled the TBI unit (old gaskets) and put it back on.
7. Used all new vacuum fittings where I could, including the caps on unused ports.
8. Removed old distributor cap and rotor. Marked spark plug wires with 1-8, in order. Got a new distributor cap and rotor.
9. Removed the distributor and spun the oil pump for about one minute.
10. Reinstalled the distributor, realized I hadn't marked it properly as to the position of the rotor.
11. Turned the engine by hand (breaker bar on crank bolt) to 10 degrees BTDC
12. Installed new rotor. Reinstalled distributor, aiming the rotor at #1 on the distributor cap.
13. Installed cap and spark plug wires, following timing 1 8 4 3 6 5 7 2 as marked on intake manifold.
14. Used Optima battery from the Wagoneer; 454 spins happily, not any indication that it's trying to fire.
15. Put the hood back on (my weightlifting workout for the day).

Whew, ok. That was last weekend.

This week, got a new battery.

1. Installed battery.
2. Jumpered fuel pump, watched pressure gauge. Steady at 13psi.
3. Removed the hood, 'cuz I knew I'd need to address the distributor. Curse those GM engineers: distributor in the back. What were they thinking!
4. Checked every connection to the TBI, coil, distributor, sensors. Everything is tight and clean.
5. Checked connector to CPU (under dash, no exposure to the elements).
6. Dropped some gas directly onto the butterfly valves.
7. Engine started for a moment, actually runs pretty smooth, and then ran out of gas.
7a. output port of injectors are bone-dry.
8. Have GF turn the key while I check voltage at injectors. Steady 9-10 volts. I thought at firing time they are supposed to pull to ground?
9. Try priming a couple more times while fiddling with distributor (timing). I think I'm close enough for it to start if it wanted to try.
9a. I thought I might have installed the distributor 180 degrees out, but if I'd done that, it wouldn't run at all, would it?

So what's happening? Is there some reason the CPU wouldn't allow the injectors to spray - a sensor is bad, or disconnected, or fuel pressure is low, or? What else can I check? I'm thinking of getting a rebuild kit and two new (not reman) injectors today.

I'm pretty much grasping at straws here now. Help!

[AwesomeJ10]

Does the coil have 12v+ with the key in both the 'on' and 'starting' position? I don't think the injectors will fire until the ECM tells them too and it won't tell them too if the coil isn't hooked up properly (I think).

And yes, the injectors receive 'ground' from the ECM when they are too fire.

[Bill usn-1]

As Blake said the ecm will not fire the injectors unless it receives the DRP-distr ref pulse from the ignition module.
Now since it starts when you put gas in that means it has spark.
So connect your timing light and open the bypass wire. The base timing on most 454's is 3.9* so you should be close to that.

Then disconnect the battery to clear codes.

If you have one, connect a test light to one of the injector connectors. red wire is + and blue or green is -.
turn the key on and you will have nothing.
hit the key and it should blink.
If not then remove the connection on the - wire and connect the test lead straight to ground and turn the key on. The light should be lit indicating you have 12v to the injector and it's just waiting for the gnd from the ECM.

If you have 12v and it blinks when you crank then the injectors are stuck.
Connect the wires and while someone cranks, tap the side of the injector pod with a handle of a screwdriver to shake it loose.

If you have 12v but no gnd from the ECM to fire them, then remove the ignition module and have it tested 4 times. If it fails any of them...replace it.

[budojeepr]

Thanks for the quick response fellas.

I'll check the coil voltage, but as Bill says if it runs the coil's got power.

Bill, you say "So connect your timing light and open the bypass wire." 'Scuse my iggerance, but what's the "bypass wire"? Is the idea here to get the timing light to come on even when the engine's not running?

I can follow the rest of your instructions (providin' it don't rain on me, it's threatening to). I think I was setting the timing too far advanced - now that I look at it the manual says 4BTDC. Then I'll check the injector wires as you say. My old test light is kaput, I'll get a new one.

Last thing - you say to remove the ignition module and have it tested quadruplegically . My manual mentions it only once, and says the ignition module is inside the distributor cap. I can't remember seeing anything like the manual says (I think their picture is for carbureted HEI) ... oops - just looked at Napa Auto Parts - MPE TP25SB looks exactly like what I'd need.

Thanks for the help, I'll get to work now.

[FSJ Guy]

[quote="budojeepr"
Bill, you say "So connect your timing light and open the bypass wire." 'Scuse my iggerance, but what's the "bypass wire"? Is the idea here to get the timing light to come on even when the engine's not running?
[/quote]

I'm not Bill, but I will reference you over to the Binder Planet's EFI FAQ. He has an excellent walk through on how to set the timining. That is what he's referring to. You disconnect the timing bypass wire and set the initial timing on your engine with the engine running.

[budojeepr]

Thanks Ethan.

Still and all, by bypass wire, we mean:

http://www.binderplanet.com/forums/show ... ostcount=3

D5, tan/blk - correct? I'm working on it now, I'll go out and see if there's a connector there, or if I have to clip the wire in order to disconnect it. Never noticed before.

[quote="budojeepr"
Bill, you say "So connect your timing light and open the bypass wire." 'Scuse my iggerance, but what's the "bypass wire"? Is the idea here to get the timing light to come on even when the engine's not running?

I'm not Bill, but I will reference you over to the Binder Planet's EFI FAQ. He has an excellent walk through on how to set the timining. That is what he's referring to. You disconnect the timing bypass wire and set the initial timing on your engine with the engine running.[/quote]

[budojeepr]

...So connect your timing light and open the bypass wire. The base timing on most 454's is 3.9* so you should be close to that.

Sorry, I'm going to need more detail. Timing light won't work if I can't get it started?

So, I took the cap off and rotated the engine 'til the rotor pointed near #1, then jogged it by hand to be 4* BTDC. Then I rotated the distributor 'til the rotor pointed right at #1, near as I could, then put the cap back on. Timing set now?

Then disconnect the battery to clear codes.

I have a main disconnect, so I used that.

If you have one, connect a test light to one of the injector connectors. red wire is + and blue or green is -.

Test light has the sharp pointy end and an alligator clip end. 'Gator to ground, pointy end in injector connector? Or should I be going from one connection in the injector connector to the other? In other words, straight across it? I guess the latter, since the first way would always light the light.

turn the key on and you will have nothing.

Right.

hit the key and it should blink.

Blinks merrily.

If you have 12v and it blinks when you crank then the injectors are stuck.
Connect the wires and while someone cranks, tap the side of the injector pod with a handle of a screwdriver to shake it loose.

Tried that, no love. While up there on the bumper, I poured a little gas in the TB and it started and ran for a moment, no backfires or lumpy running. I think the timing's pretty good for static timing.

Is there a way to unstick the injectors by removing and cleaning them? Or must I buy new ones (which I'm willing to do if necessary)?

If you have 12v but no gnd from the ECM to fire them, then remove the ignition module and have it tested 4 times. If it fails any of them...replace it.

I went ahead and replaced it; now I have a spare to test.

Thanks for the help, I'm starting to get it!

[Bill usn-1]

Each injector uses 12v which is on anytime the key is on, that is the red wire on each.
Then each inj gets a gnd from the ecm. One has a green wire and one will be blue.
It should be obvious if your looking at the injector connectors.
Remove from the injector and put the point in the red and the clip in the other.
Then turn on the key.
You will have no light.
Then crank the engine and the light should go on and off with every other cylinder firing.

If not then there is a problem.

If you do have the light then connect the conector back on the inj and then clip the probe to gnd.
Take the point of the probe and touch the injector lead with the blue or green wire.
This should apply gnd to the inj and make it click.
You may even see a little fuel dribble out the bottom.
Do not leave the probe on it. Just quick clicks.

Now this all assumes!!! that you really do have good fuel pressure after working on the TBI.
If your not sure recheck or lightly clamp some vicegrips on the return flex line to restrict the return. That will increase the pressure at the injectors.


And as long as you have someone to turn the key you can check timing while cranking.
Remember you have spark when cranking or it wouldn't start.

[budojeepr]

Hey, I got it started. I ended up buying new injectors because the old ones were - get this - rusty.

I put the new injectors in, along with a rebuild kit - again - and was able to see them spray as I cranked it. However, the liquid coming out of them didn't behave like gasoline. It kind of left droplets in the venturis. I stopped trying, cleaned everything up, and left it for the week.

Today I disconnected the hose going from the fuel pump to the TBI, connected a long piece of hose directly to the ouptut of the pump, the other end to a water jug (the OBC* drinks lots of bottled water so I have an unending supply of plastic bottles). I hooked 12V directly up to the pump so I could run it without energizing the whole ignition system.

The fuel pickup rests in the driver's side front corner of the tank, on the bottom. There are racing-type sponges in there acting as baffles. And as gunk-absorbers. Also, remember that gas floats on water. Here's what came out of the tank, starting from the left.



The two leftmost bottles are almost pure water. The third from the left is water, waxy gunk, then gas on top. The remaining bottles contain the 5 or so gallons I put in it at the beginning of this resuscitation effort. The fuel pump worked much better on the gas than either the water or the waxy gunk. I'm lucky I didn't trash the pump.

By the way, a Carter TBI pump is a good one!

I'm going to use the best of the gasoline in my junky old mower this summer. If I blow that up, no biggie.

After taking this picture, I soaked up the rest of the what was left in the tank with some old towel/rags and left them in the sun to dry. (I still need to remove the sponges from the tank and replace them, which will be a pain because it's a fuel cell with about 30 little bolts around the fillter hole which need to be removed to make room for the sponge removal.)

I put in a couple gallons of fresh unleaded and the ol' 454 fired right up.

I'm thinking the gas I bought before parking the rig had a high percentage of water in it, which separated over time and resulted in near-catastrophe. I can blame the gas station and its supplier for selling bad gas; I can blame bad timing for pumping gas from the bottom of the station's tank; but most of all I can blame my own laziness for failing to drain the tank when I parked the rig 2 years ago.

Yep, that'll do it! Lesson learned...

* OBC: Old Biddy of the Castle

[Bill usn-1]

Good to hear.
So far I have seen EFI engines fail to run on water and diesel.
I know TBI is good but it still can't overcome the basic fuel requirements.