Help! 1985 Corvette bad gas

[rodyvette]

I would like help in figuring out where to look for my solution to the problem created by letting my 1985 Corvette that sat for about 2 years. The gas turned really bad and killed the fuel pump. I replaced it and now it barely runs. Am currently trying to figure out what is still wrong. Car ran fine before sitting up. Now it barely starts and runs really rough and when I try to rev it up, it sounds like it is sucking air and then it revs but has bad miss and occasional backfire. Have replaced the fuel pump, siphoned all old gas out, though I did try to run it with the bad gas in it and then later siphoned the gas out and reached into the gas tank and wiped out as much of the crud as I could reach. Also replaced the fuel filter. Still takes a long time to start it. It just turns over and occasionally one or two cylinders fire until it finally starts. If I pour gas into the throttle body, it runs pretty good for a minute or so and then runs crappy again. Am about to pick up a fuel pressure guage to check fuel pressure. What is the order of the hunt to track down the problem?

 

[vetteboy86]

Hi there, welcome to the boards.

Pick up a fuel pressure gauge and start your troubleshooting there. A number of things could have happened while the car was sitting. A vacuum line may have become brittle and is causing a vacuum leak.

How much crap was in the tank? I've never let a car go that long, so I don't know. Have you thought about dropping the tank?

 

[rodyvette]

Thanks. I just checked it and the psi is 11 psi. I replaced the fuel pump about a week ago.

A few paper towels turned brown while wiping out the bottom. There was some thick brown stuff near the fuel pump pick up. I had replaced the fuel pump before siphoning out the old gas, so wondering if that is affecting the new pump.

 

[G Winter]

Check the sock on the pump inlet.

Glenn

 

[John Robinson]

As stated change the fuel pump sock (or screen) You might want to remove the sock and put the pump back in without it and try to start the car and see how it runs. If it runs good then get a new sock and install it the pump is OK. Because it is so easy to get to the pump this is a quick and cheap way to check the fuel delivery system while you still have your money in your pocket.

 

[rodyvette]

Good idea. I'll try that and repost my results.

 

[surfer93]

If you ran the car w/bad gas, then chances are you gummed up the fuel injectors and FPR.
Have you tried running fuel injector cleaner through?

Also, run SeaFoam through the brake hose and replace the fuel filter, it is most likely clogged.

 

[rodyvette]

I took the sock off and got 40 psi. So, I went to the parts store and bought a new sock. It went to 10 psi with the new sock.

I'm so confused.

Let me back track a little. This is with the pump i bought a few days ago. Any ideas? I was thinking the low psi had something to do with the fuel pressure regulator, but a mechanic I'm talking to is saying the low psi indicates the new pump is weak.

I bought this pump a few days ago and put it in the tank with the bad gas. Did not realize bad gas is so destructive at that time. I put the new pump in, drove it to the station and filled it up with gas, but the more I drove it, the worse it got, to the point that I barely got it home. This is with the new pump I bought a few days ago.

Now, sock off it's 40 psi, sock on its 10 psi. The more I think about it, the more it seems like the sock is telling me the pump is weak. Am I on the right track? Man, this stuff is sure discouraging.

One more back track, I have removed all the gas from the tank, wiped out as much of the bottom of the tank as I could reach and added 11 gallons fresh fuel and some Lucas injector cleaner.

 

[John Robinson]

Ok now do a pressure check with the sock off and watch the pressure and let us know how long it takes to bleed off the 40 PSI

 

[Rex S]

Fairly good chance the whole fuel system is contaminated. If you think about a carbed engine, the carb would need rebuilt and the fuel pump replaced after sitting the same period. Injectors, pump and regulator are no different. Also it is not uncommon to have a bad pump out of the box. We have had them bad from the big auto parts stores and genuine GM as well. These days being new-in-the-box doesn't really mean much.

 

[rodyvette]

what I have done now

I thought I would post a follow up, in order to help anyone else who has this problem. The car runs now. I had to replace the fuel pump and fuel filter and o2 sensor, the fuel gauge sending unit, and I had to replace the fuel pump 3 times. I think the problem was that the bad gas had not only killed the fuel pump, but it also deteriorated the rubber coupling that connects the fuel pump to the fuel line on the sending unit. The 3rd fuel pump was an AC Delco and it had a fuel line and clamps included. The other fuel pumps didn't have the new fuel line and clamps, so I was just reusing the old rubber coupling. I think this is why the other 2 new fuel pumps were only giving me 5 to 10 psi. Once I put in the AC Delco fuel pump and attached the fuel line with the new rubber hose and clamps, I got 33 to 36 psi constantly. That was a huge big deal. I had been chasing my tail trying to figure out why the car was running so horribly and it was definitely the low psi, which I think was caused by the new fuel pump not being able to deliver the fuel at the right psi, due to a leaky coupling in the tank. I think the first two new fuel pumps I installed were probably giving 35 psi, but 25 to 30 of that psi was just lost in the tank due to a weak coupling. So, if you are replacing your fuel pump due to bad gas killing it, be sure to also replace the coupling that joins the fuel pump to the sending unit fuel line. If you don't, that little detail may cause you to replace a bunch of stuff you don't need to replace, and, if you are like me, say a bunch of words that make your wife and kids go hide in the house. To further clarify, the coupling I am referring to is a little metal piece that is about an inch long and has rubber inside of it. It slides over the fuel pump "gas out" port and also slides over the fuel line on the sending unit, connecting the fuel pump to the fuel line. The weakest link scenario applies here. This little piece cost me a weekend and tons of frustratoin and could have caused me to tear into my motor. When replacing your fuel pump, be sure to use rubber gas line and clamps to attach the fuel pump to the fuel line and you will ensure you get all the 35psi to your fuel rail. So, to wrap up my adventure, The bad gas killed the old fuel pump and the fuel guage sending unit thing that makes the gas guage read out on your dash. I replaced that fuel pump and ran the bad gas through the car and I think that killed the o2 sensor. Siphoned all fuel out, wiped the tank, put in fresh gas, replaced the fuel pump a total of 3 times before I figured out the coupling was causing the fuel pressure to be lost in the tank where the fuel pump is coupled to the sending unit. Once I figured that out, and once I replaced the o2 sensor, all is well again.

 

[avp0713]

re: 1985 Corvette bad gas. . .

Rodyvette -

Would you happen to have taken any pictures of this whole event?

situation:
I've decided to bring my 1985 Vette back from the dead..oops, I mean driveway spot that it's been sitting in for the last 10 years.

Have replaced many engine parts...

Replaced fuel filter, fuel pump, drained out tank, wiped away all the orangy/brown sludge in the tank. I am getting a new(used) fuel sending unit this weekend (April 2, 2011).. I want to make sure I don't run into the same issue (bad coupling and hose) that you had (and resolved). If possible can you take a picture of this coupling? and perhaps post it up?

Thanks
Tony
Brick, NJ (Jersey shore)

 

[boomdriver]

I thought I would post a follow up, in order to help anyone else who has this problem. The car runs now. I had to replace the fuel pump and fuel filter and o2 sensor, the fuel gauge sending unit, and I had to replace the fuel pump 3 times. I think the problem was that the bad gas had not only killed the fuel pump, but it also deteriorated the rubber coupling that connects the fuel pump to the fuel line on the sending unit. The 3rd fuel pump was an AC Delco and it had a fuel line and clamps included. The other fuel pumps didn't have the new fuel line and clamps, so I was just reusing the old rubber coupling. I think this is why the other 2 new fuel pumps were only giving me 5 to 10 psi. Once I put in the AC Delco fuel pump and attached the fuel line with the new rubber hose and clamps, I got 33 to 36 psi constantly. That was a huge big deal. I had been chasing my tail trying to figure out why the car was running so horribly and it was definitely the low psi, which I think was caused by the new fuel pump not being able to deliver the fuel at the right psi, due to a leaky coupling in the tank. I think the first two new fuel pumps I installed were probably giving 35 psi, but 25 to 30 of that psi was just lost in the tank due to a weak coupling. So, if you are replacing your fuel pump due to bad gas killing it, be sure to also replace the coupling that joins the fuel pump to the sending unit fuel line. If you don't, that little detail may cause you to replace a bunch of stuff you don't need to replace, and, if you are like me, say a bunch of words that make your wife and kids go hide in the house. To further clarify, the coupling I am referring to is a little metal piece that is about an inch long and has rubber inside of it. It slides over the fuel pump "gas out" port and also slides over the fuel line on the sending unit, connecting the fuel pump to the fuel line. The weakest link scenario applies here. This little piece cost me a weekend and tons of frustratoin and could have caused me to tear into my motor. When replacing your fuel pump, be sure to use rubber gas line and clamps to attach the fuel pump to the fuel line and you will ensure you get all the 35psi to your fuel rail. So, to wrap up my adventure, The bad gas killed the old fuel pump and the fuel guage sending unit thing that makes the gas guage read out on your dash. I replaced that fuel pump and ran the bad gas through the car and I think that killed the o2 sensor. Siphoned all fuel out, wiped the tank, put in fresh gas, replaced the fuel pump a total of 3 times before I figured out the coupling was causing the fuel pressure to be lost in the tank where the fuel pump is coupled to the sending unit. Once I figured that out, and once I replaced the o2 sensor, all is well again.

If this was from fuel from 2008-9 then its understandable.
Alcohol blends back then were different than today and so was the rubber.Back then there was the summer blend and the winter blend. one was o2 or N enriched and the other had a good dose of MTBE. An alcohol blend (ethanol) is now standard for most if not all states. As that evolved so did the rubber fuel lines, o-rings and other things.
The MTBE (meth for cars) would attack many rubber parts and harden the part, and cause it to decompose super fast. The fuel pump impeller is rubber. Also, the meth or alcohol acts as a catalyst for water and gasoline so water will now mix with gas. Leaving a fuel tank sitting still for a few months will cause condensation to form from temp changes and the alcohol allows the water to remain and cause rust all thru the system. I've seen fuel senders and pick-up tubes that were covered with rust. I personally mopped out about 3 tablespoons of rust in my tank once I realized that I had a problem. So its easy to see how the pump got trashed sending solid rust particles thru the lines and how the adaptor hose in the tank degraded.
If it were me, I'd plan on changing the fuel filter again real soon and think about new injectors as well. Rust particles can be small enough to get past the sock to the filter and even beyond. Thats not to mention anything that was dissolved in the fuel that made it past the filter into the rails. Your fuel regulator having a rubber diaphram might be at risk too..If you can smell fuel in the vac hose from the regulator or its wet with gas...the diaphram is broken and leaking. The engine will run rough as well from the raw gas in the intake.
The injectors each have a fine screen (basket) inside to catch stuff before it can damage the pintle or nozzel and effect the spray pattern...thing is, when the basket plugs up the flow is reduced so the spray gets screwed up anyway. Since upgrade injectors are only $250 from FIC, its a good investment in a fuel system thats been damaged.
I'll bet you were glad to hear that thing fire up after 2 yrs...
Good luck with it! its the time of year to enjoy !

 

[WhalePirot]

I'd wonder if the first two pumps were okay, after all. When I switched to TPI from TBI, I would those rubber coupling hoses burst from the higher pressure; thankfully, inside the tank, not outside.

I have cleaned an O2 sensor with a torch. I'd not be surprised to see it fouled with the ECM trying to adjust for all that fuel pressure variation and the consequent rich/lean conditions.

Glad you got it running and learned a few things along the way.