My J-4500

[Crankyolman]

Well today was a nice warm fairly clear non rainy day so I decided I was going to take the truck to work.



It didn't go well.


My drive to work is only 6 mile and halfway there way there going up a big hill I suddenly lost power, If I tried to give it any gas at all it just bogged and lost power. I pulled over and after a couple of restart attempts got it running again and continued. It ran good as long as I kept it around 40MPH (2,000 RPM or so) but whenever I came to a light or even had to slightly slow down it would lose all power and sometimes die and it was trying to overheat.

The light just before work it got up to 225f but ran very well for some reason.

At work I checked the radiator and found it low so I topped it up and started it and it ran fine. I figured it was that I was low on gas because the tank only had 2 gallons.

When I got out of work I had my wife meet me at the gas station and we filled both the truck and escape. It ran fine to the gas station but as soon as I started it up there it started popping through the carb...well fuel injector and dying. I drove it home but it didn't drive well. I had to keep the throttle up or it would die. Sometimes it would pop through the carb and when it died it would take several attempts to get it running and I would have to go like hell to keep it that way.

Eventually I got it home and at home it seems to idle fine but any throttle at all caused it to pop and sputter. So now I need to figure that out and really have no clue where to begin because it was fine before it sat for a couple months while I painted it.

[SOLSAKS]

dang, got to be something simple.

let us know what you find.

dave in NC

[Crankyolman]

dang, got to be something simple.

let us know what you find.

dave in NC

I posted a link to the data log in the fuel injection section, (http://www.ifsja.org/forums/vb/showthread.php?t=188956 )

Hopefully someone who knows that stuff can help. I'm going to go pull the fuel filter out and clean it and see if that's the problem, hopefully that's all it is but I don't have a lot of faith.

[78 WIDETRAC]

I'll pm you about the bumper

[Crankyolman]

I'm so frustrated and depressed over this problem right now I'm seriously regretting keeping the AMC engine and not doing a basic small block Chevy swap. Money is getting tighter by the day and the truck is already way over budget and really needs to be running. The way I feel right now I'd sell the truck if I could get anywhere near what I have in it but an old broke down Jeep truck ain't worth squat if it ain't running.

[DarkMonohue]

My drive to work is only 6 mile and halfway there way there going up a big hill I suddenly lost power, If I tried to give it any gas at all it just bogged and lost power. I pulled over and after a couple of restart attempts got it running again and continued. It ran good as long as I kept it around 40MPH (2,000 RPM or so) but whenever I came to a light or even had to slightly slow down it would lose all power and sometimes die and it was trying to overheat.

The light just before work it got up to 225f but ran very well for some reason.

At work I checked the radiator and found it low so I topped it up and started it and it ran fine. I figured it was that I was low on gas because the tank only had 2 gallons.

When I got out of work I had my wife meet me at the gas station and we filled both the truck and escape. It ran fine to the gas station but as soon as I started it up there it started popping through the carb...well fuel injector and dying. I drove it home but it didn't drive well. I had to keep the throttle up or it would die. Sometimes it would pop through the carb and when it died it would take several attempts to get it running and I would have to go like hell to keep it that way.

Eventually I got it home and at home it seems to idle fine but any throttle at all caused it to pop and sputter. So now I need to figure that out and really have no clue where to begin because it was fine before it sat for a couple months while I painted it.

Boldface added at key points.

It ran fine before you painted it - i.e. it ran fine before it was disassembled. Don't change the tune. You have a physical problem that needs to be corrected.

All of the behavior you described points toward a lean condition. Is there a vacuum hose loose or missing? Is there any chance the electrical connections to the fuel pump, throttle position sensor, or injectors are loose or broken? How about wiring? Did any wires get stretched, stressed, pinched during disassembly or reassembly? Any chance of moisture in the connectors?

I'm so frustrated and depressed over this problem right now I'm seriously regretting keeping the AMC engine and not doing a basic small block Chevy swap. Money is getting tighter by the day and the truck is already way over budget and really needs to be running. The way I feel right now I'd sell the truck if I could get anywhere near what I have in it but an old broke down Jeep truck ain't worth squat if it ain't running.

The problem is almost certainly something around the engine, not the engine itself. This is not an AMC problem. Swapping to a bellybutton engine would neither prevent nor correct it.

The money is spent. Try not to worry about that. It has nothing to do with this problem. Anyway, I bet it won't cost much to fix. It really sounds like an assembly error or a simple wire or hose issue.

[Crankyolman]

Boldface added at key points.

It ran fine before you painted it - i.e. it ran fine before it was disassembled. Don't change the tune. You have a physical problem that needs to be corrected.

All of the behavior you described points toward a lean condition. Is there a vacuum hose loose or missing? Is there any chance the electrical connections to the fuel pump, throttle position sensor, or injectors are loose or broken? How about wiring? Did any wires get stretched, stressed, pinched during disassembly or reassembly? Any chance of moisture in the connectors?

As far as the engine the only thing related to it that was disturbed during the rapaint was the fuel tank and those wires were never disconnected but I will check them today and see if anything is loose. I checked all the vacuum ports and don't find anything wrong there. In the past I've had issues with deteriorated vacuum caps so these aren't that old and look fine. According to the data log the vacuum is right where it has always been, around -17-18 and AFR is 14.3 except just after I let off the gas and it starts struggling to stay running the RPM dropped to as low as 242, vacuum dropped to -4 and AFR went to 20. One thing is it seems to run fine when cold but once it hits the temperature where the FI goes into self learn mode is when it starts acting up, that's something like 150f.

The problem is almost certainly something around the engine, not the engine itself. This is not an AMC problem. Swapping to a bellybutton engine would neither prevent nor correct it.

The money is spent. Try not to worry about that. It has nothing to do with this problem. Anyway, I bet it won't cost much to fix. It really sounds like an assembly error or a simple wire or hose issue.

That was me being frustrated but there are actually a lot of advantages to an SBC vs an AMC when it comes to Fuel injection.


I just thought of this, while the truck was sitting the battery went completely dead, to the point the doors wouldn't unlock remotely and I had to jump start it and recharge the battery. Thinking back it didn't start as quickly as normal and may have even died when I moved it, something I attributed to the low fuel condition.

[DarkMonohue]

One thing is it seems to run fine when cold but once it hits the temperature where the FI goes into self learn mode is when it starts acting up, that's something like 150f.

At that temperature it's probably also going into closed loop operation and looking for feedback from the oxygen sensor. If I read your data logs correctly, the fuel trim was getting higher and higher, so it may have been reading a false lean condition and adding more and more fuel to correct that. Or maybe it actually was lean and was struggling to fuel adequately. Since this seems to happen only in closed loop, I doubt that is the case.

I'd start with the o2 sensor wiring as well as making sure there are no exhaust leaks upstream of or in the vicinity of the sensor. It is tempting to see a value on the data log and assume that it is a functional sensor reporting real data correctly, but sometimes dead or disconnected sensors can be less than obvious.

It would definitely be nice to have factory EFI components and manifolds that were designed to take advantage of ram tuning, like the old TPI. But that's a separate issue from your driveability problem.

[Crankyolman]

The other day when the truck was at work I did a walk around photo shoot so I thought I would give you guys the experience. This also reminds me how much I love my truck.

[Crankyolman]

I'd start with the o2 sensor wiring as well as making sure there are no exhaust leaks upstream of or in the vicinity of the sensor. It is tempting to see a value on the data log and assume that it is a functional sensor reporting real data correctly, but sometimes dead or disconnected sensors can be less than obvious.

I'll do that. I don't find any leaks but I'm currently using that clamp on bung for the O2 sensor, which many people have had problems with and I've never liked. I've never really been happy with the exhaust system in general because even though it was new when I bought the truck they failed to loop it over the axle, all they did was a little bit of a joggle, maybe 3 inches to get it over the axle and if it's loaded with 500 pounds of apples the exhaust actually contacts the bolt that holds the brake line to the axle. I've been meaning to fix that for a long time so maybe now is the time to cut the exhaust apart, shorten it up so it exits ahead of the wheel and TIG weld it all back together along with welding the bung in place.



I need to figure out what easily accessible O2 sensor I can replace the one they provided with so I can buy one local and see if that makes a difference.

[DarkMonohue]

There are only a few basic types of oxygen sensors. Is yours wideband or narrowband? Heated or not? How many wires?

I also have some extra bungs here. Let me know if I can send you one.

[rang-a-stang]

Your truck looks next level awesome now! Wow! The grill with the 4 headlights looks SOOoooo great!

I think your fueling problems are in your fuel pump/regulator (like babywag said in the other thread). You EFI relies on steady fuel pressure (even as fuel demand increases) and as it drops, your truck runs lean, your EFI tries to add fuel by extending the fuel pulses but that does not work because your pressure is so low.

That's my guess.

[Crankyolman]

There are only a few basic types of oxygen sensors. Is yours wideband or narrowband? Heated or not? How many wires?

I also have some extra bungs here. Let me know if I can send you one.

OK, I gave everything a good looking over and found no exhaust leak or signs of one. I found a website that says



[quote=other website]
FiTech currently uses a Bosch LSU 4.2 oxygen sensor, also referred to as an O2 sensor. FiTech recommends using a replacement sensor from a

[DarkMonohue]

I believe that's a wideband sensor, and likely the same one the Innovate LC-1 wideband controller in my other car uses.

Does FiTech give you the means to stay in open loop mode so that you're running just on the base tables and not trying to trim mixture based on sensor feedback?

Do they give you a procedure to calibrate the wideband sensor?

[Crankyolman]

Your truck looks next level awesome now! Wow! The grill with the 4 headlights looks SOOoooo great!

Thank you, I'm very happy with how it looks


I'll address the fuel pump issue over in the other thread when I have time.