91 Nissan, need help.

[AyWoSch Motors]

I know it isn't a squarebody, or a chevy, or even American, but you guys are all super helpful and thought you may be able to help.
It's not my truck, it's my buddy's. 91 Nissan 4cyl, 5 speed stick, 2wd.
I helped him get it running a few weeks ago, and the past few days, it started running like crap, and we cant figure out why.
It was his Dad's, his dad died, and it had been at his family property. Hadn't run in 5 years, we flat towed it back to his house. It needed a battery, a starter, and a fuel pump. After changing out the pump, it started right up and ran beautiful, we took it out for a drive and it ran and drove great.
Now, when you start it up, it runs fine for about 30 seconds, then starts to spudder and spit, and cut out worse amd worse until it dies. If you try to drive it, its pops and spudders and bucks. Its starts off fine, running on 4, then sounds like its running on 3, then sounds like it's running on 2 (sounds like a wicked cam in a big block), then it pops a little like its running on 1, them dies. Has no power at all. When its just idling, itll stay running, but if you put any load on it, it hates it.
We've checked that the pump is working, the lines aren't clogged, the filter isn't clogged, that the air flow sensor is clean, it has new distributor cap, wires, plugs, we cleaned the injectors and checked them with an ohms meter to make sure they're working. The ECU isn't showing any problem codes.
All we can think of is that either there is a sensor or something that's gone bad, or the ECU is crapping out.
I thought maybe it could be the new fuel pump isn't putting out the right fuel pressure, but it's new, so...
And i thought maybe the coil isn't putting out enough, but that wouldn't explain why I runs great at first then not.
I dont know, we're both stumped. Any help you can offer would be awesome, thanks.

 

[AyWoSch Motors]

Dont know why that doubled the thread, sorry.

 

[yevgenievich]

Does it have a port to check fuel pressure?

 

[Rusty Nail]

How much 5 year old gas are you attempting to burn?

 

[ebodell08]

Sounds like crappy fuel possibly?
I bought one of those 5 yrs ago off of CL for $200, replaced the motor and donated it to a local rescue. I had a similar experience, mine turned out to be the disty. Far as I know it is still running around. They are decent little trucks.

 

[Bruce Wingate]

Sounds like crappy fuel possibly?
I bought one of those 5 yrs ago off of CL for $200, replaced the motor and donated it to a local rescue. I had a similar experience, mine turned out to be the disty. Far as I know it is still running around. They are decent little trucks.

Possibly crappy fuel delivery too - check the fuel filter and change if needed

If you can, try running it off a gas can by running a line from the can to the [Mechanical?] fuel pump. You may end up dropping the gas tank and cleaning it out.

 

[AyWoSch Motors]

Does it have a port to check fuel pressure?

I dont believe so, I looked. He doesnt have a fuel pressure tester either. I thought it may a fuel pressure issue too.

How much 5 year old gas are you attempting to burn?

About 2 Gallons. I told him we should dump it, but he said itll be fine. We added 3 gallons of fresh that night, and then 5 the next morning.

Possibly crappy fuel delivery too - check the fuel filter and change if needed

If you can, try running it off a gas can by running a line from the can to the [Mechanical?] fuel pump. You may end up dropping the gas tank and cleaning it out.

I thought about trying to run it off a bottle, but it has an in tank electric pump.
He said he checked and cleaned the filter, but didn't change it.

 

[yevgenievich]

Drop/check fuel tank or set up for testing fuel pressure to eliminate it. Ignition worth verifying as well.

 

[Rusty Nail]

1991 Nissan ..

They got timing chains, not belts.. Good luck fixin it.
I'm still at the fuel and would not be quick to drive it lmao..it gets 800 miles a gallon man, i'd see if I could get it to burn gas...let it run and watch the temp. See if you can get the thermostat to open man, it's 95 degrees outside, that car aint been run in five years and youre forcing bad gas down it's throat.

Let it wake up!

 

[Rusty Nail]

1991 Nissan ..

They got timing chains, not belts.. Good luck fixin it.
I'm still at the fuel and would not be quick to drive it lmao..it gets 800 miles a gallon man, i'd see if I could get it to burn gas...let it run and watch the temp. See if you can get the thermostat to open man, it's 95 degrees outside, that car aint been run in five years and youre forcing bad gas down it's throat.

Let it wake up! I'm still at the gas.

 

[AyWoSch Motors]

Drop/check fuel tank or set up for testing fuel pressure to eliminate it. Ignition worth verifying as well.

Yeah, it looks like were gonna have to at this point. Dang.
I told him we should be dumped that old crappy gas.
I wanted to test the coil, but he said its fine. Everything between the coil to the engine is new.

 

[AyWoSch Motors]

So an update on this one...

After my last message, my friend just gave up on it, and let it sit in the backyard. But just the other day, he asked if I could fix it for him. Said hed trade me for some free welding, so I said sure.
... now its sitting in my backyard.

I threw a battery in it, and gave it a try. Still same thing.
So far I've diagnosed, that its definitely a fuel delivery issue.
I bottle fed it, and it ran fine. As soon as I stopped, it died.
I realized he had cut the catalytic converter off it, and I cant help but wonder if it's the O2 sensor sending a false signal to the computer to lean it out.

I figure it's either bad fuel pressure, from the after market pump, impeded fuel flow from a feul filter, a bad feul pressure regulator, the injectors are dirty, or everything is working as it should, and the injectors aren't getting the proper pulse signal from the computer.
Those are my new thoughts. I have to read the computer again, and do some other diagnosing, and maybe some parts replacement. But any one have any new thoughts?

 

[fast 99]

Go back to basics, spark, fuel, compression. If good compression and decent spark, check injector pulse either with a test light or noid light. Possible, the injectors are stuck. Try using one of those vibrating engravers on each injector. Sometimes it will kick them loose inside. Bad fuel will stick valves most of the time it will be an intake.

 

[Joe Voter]

If it's not the gas I bet its the battery cables.