Massive backfiring, car hard to start

[TurboTer]

Everything on the '85 GN has been fine but yesterday it started backfiring from the front a lot. Within about two minutes or so, it got so bad I couldn't go more than 3 miles an hour or so. There was a hill and the car didn't make it, and stalled, so I towed it to my house. Car takes time to start, and when it finally does, there's that massive backfiring again and then it stalls. Before anyone asks, there is a half a tank of gas in the car. I haven't done anything to the car in a while, so any ideas as to what it can be?

 

[V6 Beast]

Sounds like maybe the cam sensor. After getting it started unplug the cam sensor and see if it smoothes out. You will have to plug cam sensor back in to get it to start.

Sully

 

[TurboTer]

Originally posted by V6 Beast
Sounds like maybe the cam sensor. After getting it started unplug the cam sensor and see if it smoothes out. You will have to plug cam sensor back in to get it to start.

Sully

I'll try, but it seems like the car has gotten worse. I mean, now when it finally starts it stalls after about 3 seconds.

 

[gn85]

I'm also wondering if a MAF went south on ya?? What diagnostic measures have ya tried?? As mentioned, a cam sensor is a very likely cause as well.

Fuel pressure OK? Where you getting on it when it started backfiring??

 

[V6 Beast]

It's getting worse because it keeps sliding and getting farther out of adjustment. Pretty soon won't start at all. You can pull the cap and look for little pieces of metal stuck to the magnets in the cap.

Sully

 

[TurboTer]

Originally posted by gn85
I'm also wondering if a MAF went south on ya?? What diagnostic measures have ya tried?? As mentioned, a cam sensor is a very likely cause as well.

Fuel pressure OK? Where you getting on it when it started backfiring??

One thing to note: I put on an adj. fuel pressure regulator about a week ago, but took it off because it leaked. I put back the stock 233 and it's been fine since.

Don't have a scan tool yet, but I have a fuel pressure guage. Was reading normal (28 or so) since I installed it 2 months ago, but I looked really quick before it stalled today and it looks like it said only about 5.

I was driving normal when it was backfiring. There was some traffic (rush hour) so I imagine that I did no more than 35 mph.

 

[gn85]

Fuel pressure only made it up to 5?? Can you run the pump without the car running and see what the FP gets up to?

 

[TurboTer]

Originally posted by gn85
Fuel pressure only made it up to 5?? Can you run the pump without the car running and see what the FP gets up to?

You mean with the key in accessary position? Reads 0. Just tried to start the car again. After a while it started and stalled in about 2 seconds, not long enough for me to make it to the fuel guage under the hood.

 

[striker_29]

The backfiring really makes me think cam sensor, or maybe maf. Low to no fp though sounds like the pump going south to me Ter.

 

[gn85]

Originally posted by TurboTer
You mean with the key in accessary position? Reads 0. Just tried to start the car again. After a while it started and stalled in about 2 seconds, not long enough for me to make it to the fuel guage under the hood.

Well, with the key in and turned to the "ON" position, your fuel pump should come on for two seconds then stop. That should be enough time to prime the fuel rail and see decent pressure. I was also wondering if you had a way of running the pump continously. I can't remember where the primer plug is on the 85 GN. Do you have a hot-wire kit on this car for your fuel pump???

I would turn the key on (after it's been off for a min) and listen for the fuel pump running. Perhaps have someone turn the key while you listen out back. What could be happening is that your fuel pump or relay has died and when you start the car it's sucking in just enough fuel to fire and die.

 

[xlr8ngn]

It may have jumped timing if you have not replaced the timing chain. When I replaced mine, it was still running fine but there was a pile of nylon teeth in the bottom of the oil pan.

 

[TurboTer]

Originally posted by striker_29
The backfiring really makes me think cam sensor, or maybe maf. Low to no fp though sounds like the pump going south to me Ter.

I'm really thinking it's the pump now. Now when it starts it stalls almost right away. With the key turned, I am getting 0 fuel pressure. It probably has the original 1985 pump in it. I ordered a Walbro 340 with hotwire kit. Even if it's not the pump, I am gonna need the Walbro anyway.

 

[TurboTer]

Originally posted by gn85
Well, with the key in and turned to the "ON" position, your fuel pump should come on for two seconds then stop. That should be enough time to prime the fuel rail and see decent pressure. I was also wondering if you had a way of running the pump continously. I can't remember where the primer plug is on the 85 GN. Do you have a hot-wire kit on this car for your fuel pump???

I would turn the key on (after it's been off for a min) and listen for the fuel pump running. Perhaps have someone turn the key while you listen out back. What could be happening is that your fuel pump or relay has died and when you start the car it's sucking in just enough fuel to fire and die.

Nah, no hotwire. The fuel pump is 100% stock in every way. I just ordered a Walbro 340 w/ hotwire, so hopefully it'll come by Saturday. I don't hear anything when I turn the key.

 

[gn85]

Originally posted by TurboTer
Nah, no hotwire. The fuel pump is 100% stock in every way. I just ordered a Walbro 340 w/ hotwire, so hopefully it'll come by Saturday. I don't hear anything when I turn the key.

Yep, sounds like a fuel pump might have gone south. That or a relay. Do you still have the idiot light for oil pressure, because then it would have kept supplying power to the fuel pump. When it was sputtering and backfiring, it was probably way low on fuel pressure and the vacuum from the engine was doing like a carb and pulling about 3-5 psi of fuel in.. just enough to sputter and spit.

Regardless, sounds like your going to replace them both anyways. Hope that's the prob.

 

[V6 Beast]

Originally posted by TurboTer
I'm really thinking it's the pump now. Now when it starts it stalls almost right away. With the key turned, I am getting 0 fuel pressure. It probably has the original 1985 pump in it. I ordered a Walbro 340 with hotwire kit. Even if it's not the pump, I am gonna need the Walbro anyway.

You did check to make sure you had gas in tank and your sending unit for the gauge wasn't stuck showing gas on gauge when tank was empty right?

 

[TurboTer]

Originally posted by V6 Beast
You did check to make sure you had gas in tank and your sending unit for the gauge wasn't stuck showing gas on gauge when tank was empty right?

Well, the night before I drove home from work fine. I should have gotten gas that night, but didn't. The next day, when I entered the car, it started and stalled. I looked and the gas was on "E", so I figured it was near empty. After several tries to start it, it finally started, and I drove to the nearest gas station (1 minute away) and got $15 of 93 octane (which I always get). So I left and though to myself "Whew! That was close!" But I spoke too soon. Five minutes later, it started backfiring from the front. Within a minute, it would go no more than 5 miles per hour or so. Finally, it stalled while trying to go up a hill, and I had it towed to my home. The more I'm thinking, I now think it could be a clogged fuel filter. Any thoughts?

 

[V6 Beast]

Well... with this NEW information, I would think you may be correct. Cheap and pretty easy to change.

S.

 

[TurboTer]

Update: I was wrong about not hearing the fuel pump when I turn the key. I do hear it. To me it sounds a bit different than it used to, but it could be my imagination. Just put a 237 regulator on, and same problem (starts up, then stalls). Still getting 0 fuel pressure (or damn near 0) though. Will try the fuel filter next.

 

[TurboTer]

Originally posted by V6 Beast
Well... with this NEW information, I would think you may be correct. Cheap and pretty easy to change.

S.

The only problem with that is wouldn't it be awful strange for it to be working fine one day, and clogged the next? If would have to be some sort of massive clogging. Now, I don't have a lock on my gas tank, so the only thing I could think of is someone could have put something in my tank? Oh well, I'm off to the store to get one. Cross your fingers.

 

[JDEstill]

I've had a fuel filter plug up within a day or so of filling up, though not so bad to keep the car from running, just bad enough to make the car fall on its face with any boost at all.

I've also had my stock fuel pressure regulator fail, and it gave me nearly zero fuel pressure and the car wouldn't run. That time I took a C clamp and tightened down on the rubber part of the return line, just enough to allow some fuel pressure to build but not enough to stop the flow through the line completely. It was enough to get me home (halfway across Houston!).

John