Massive backfiring, car hard to start

[TurboTer]

I was just outside and it's not my imagination. When I turn the key, the feul pump definatly makes a different sound. It now has more of a clicking sound then a straight, one sylabal (sp?) sound. While I'm on the subject, where exactly is a fuel filter on a hotair? It was in full view on my old '87 GN on the driver's side, in front if the back wheel. It's over 90 degrees outside and I don't wanna search all over for it.

 

[gn85]

Fuel filter is up front, near the engine. Follow the fuel lines coming off the fuel rail and it'll go straight to it. If I remember right, it's the same fuel filter as the 86/7.

As for your fuel filter sounding funny... one of a couple things could have happened. As mentioned before, your fuel filter could have just clogged RIGHT up. Remember, when you run the car out of gas like that, the last gas you are drawing through the lines can try to pick up all the dirt and crap in the tank. Also, don't forget that you have a fuel sock on the fuel pump. That could have collapsed. Lastly, the fuel pump could have cavitated with the absence of fuel.

 

[TurboTer]

Originally posted by gn85
Fuel filter is up front, near the engine. Follow the fuel lines coming off the fuel rail and it'll go straight to it. If I remember right, it's the same fuel filter as the 86/7.

As for your fuel filter sounding funny... one of a couple things could have happened. As mentioned before, your fuel filter could have just clogged RIGHT up. Remember, when you run the car out of gas like that, the last gas you are drawing through the lines can try to pick up all the dirt and crap in the tank. Also, don't forget that you have a fuel sock on the fuel pump. That could have collapsed. Lastly, the fuel pump could have cavitated with the absence of fuel.

You make good points. Couldn't change the filter today or yesterday because of work. I will do so Sunday. I breifly checked before work and saw where it's located. A tad bit difficult to get to without a lift, but I can manage it. I'm thin.

One question though: If it's just the filter, why is my pump sounding funny when I turn the key? Wouldn't that automatically indicate bad pump, or could it be sounding funny because fuel can't pass thru because the filter is clogged?

 

[49-blues]

Teri- stop by my girls house on sunday afternoon and we ll throw in the new filter- i forgot i ll have to run it over to you-matt

 

[gn85]

Originally posted by TurboTer
You make good points. Couldn't change the filter today or yesterday because of work. I will do so Sunday. I breifly checked before work and saw where it's located. A tad bit difficult to get to without a lift, but I can manage it. I'm thin.

One question though: If it's just the filter, why is my pump sounding funny when I turn the key? Wouldn't that automatically indicate bad pump, or could it be sounding funny because fuel can't pass thru because the filter is clogged?

It could be the sound of the pump dead heading against whatever obstruction there is. Of course, it is difficult to tell because I can't hear the noise and didn't really know what it sounded like originally. As I said before, if the pump cavitated then that would make it sound different. At least since you've heard it running you can confirm it's not an electrical problem.

As you said, you're going to change your fuel pump and hot-wire anyways.. I'm not sure how much I'd trust the original stocker that has obviously had some sort of problem as well.

 

[TurboTer]

Originally posted by gn85
It could be the sound of the pump dead heading against whatever obstruction there is. Of course, it is difficult to tell because I can't hear the noise and didn't really know what it sounded like originally. As I said before, if the pump cavitated then that would make it sound different. At least since you've heard it running you can confirm it's not an electrical problem.

As you said, you're going to change your fuel pump and hot-wire anyways.. I'm not sure how much I'd trust the original stocker that has obviously had some sort of problem as well.

I just changed the filter. The car started, then keeps stalling. I kept it running for like a minute by giving it a little gas and Matt told me it was reading near 0 on the fuel pressure guage. It really sounds like the pump to me, and it's still making that odd sound. Do you think it could be anything else? I don't see how, with the pressure reading so low (and the filter and regulator changed).

 

[gn85]

Originally posted by TurboTer
I just changed the filter. The car started, then keeps stalling. I kept it running for like a minute by giving it a little gas and Matt told me it was reading near 0 on the fuel pressure guage. It really sounds like the pump to me, and it's still making that odd sound. Do you think it could be anything else? I don't see how, with the pressure reading so low (and the filter and regulator changed).

Yah.. you've taken out pretty much everything in the system. The only other possibility (but it seems remote to me) is that one of the rubber lines are pinched off. There are rubber lines on the DS where it couples to the metal fuel lines in the frame rail. (so the engine can move around). Then there are rubber lines above the rear axle. Once again, that would strike me odd if that were the case. Lastly, there is a 'pulsator' in the tank that connects the fuel pump to the hangar in the tank. This is supposed to keep the fuel pump quiet. If that leaked, it would cause your FP to drop.

When you change the fuel pump, remember there is a fuel sock ON the fuel pump. It's worth it to replace that while you have the tank open. Make sure you get a good one that has ribs inside so it won't collapse. Also, I use a fuel injection line and clamps on the fuel pump in place of the 'pulsator'.

Empty the tank out before you try to drop it... without the fuel pump working, that's not going to be fun. Good luck.

 

[Turbo__Tim]

TurboTer, I had the exact same problem, run for 5 minutes, then backfire through the intake. The problem was the crank sensor.

If the problem is not fuel related do this...

Check to see that the interrupter rings in the pulley are not touching the sensor. Check through all 3 rings!.

What was happening was one of the rings was bent and rubbing the sensor. Apparently this caused it (the sensor) to overheat. Had to yank the pulley, and re-bend the ring to get it bent back into it's original shape.

Even if you find the sensor is adjusted correctly, and not rubbing, I would change it anyway. Just because the symptoms are so similar. In all the time I have been reading (and researching) this board I have never seen these exact symptoms described, except for when I had this problem.

Crank sensor, or the adjustment of same..

 

[gn85]

UPDATE??

Any update on this?? I had to dig several pages back to find this thread. I can't imagine the car is sitting and not running all this time.

 

[TurboTer]

Re: UPDATE??

Originally posted by gn85
Any update on this?? I had to dig several pages back to find this thread. I can't imagine the car is sitting and not running all this time.

Believe it or not, I'm still waiting for the Walbro 340 fuel pump to arrive (today makes two weeks since it was ordered by Pay Pal). It went out on July 4th (from Canada), and should be here this week. I will keep you posted.

 

[TurboTer]

Update!

On Thursday, the Walbro 340 w/ hotwire was put it. Well, the car is fine now, so that was the problem. Car is reading about 42 pounds of pressure now (the only mods are in my sig).

Not getting off topic too much, but the KM 3" downpipe and exhaust in my sig, along wiith a 160 degree thermo, will be installed this week, and hope to get to the track next week. Any ideas what my times might be?