Fuel Pump/Heat Issues

[RiggerRob]

About 2 months ago I was filling up my 'new' '84 and noticed a pretty bad gas smell inside the car. I checked the fuel lines and fuel pump, and - sure enough - there was quite a bit of gas coming out of the bottom of the fuel pump. I headed out to my 'Tercel graveyard' and pulled the fuel pump off of my '86 FWD as I had a long road trip the following day and didn't want to leak fuel all over the place.

So, here's where the fun begins: any time I stop the car for, oh, say, an hour or less in hot weather and then try to take off again, the engine stalls out and shows typical symptoms of being fuel starved. I have to pull off the side of the road and let it idle for a bit before it starts behaving again. I've noticed that if I baby the throttle I can usually get to where I'm going okay, but in this hot weather it has become an increasing nuisance, especially when merging into rush hour traffic in Charlotte. I live on a pretty steep hill in Asheville and it was threatening to stall on me on the way home today - not a good situation on a curvy mountain road with no pull-offs!

Here's the thing: I didn't really have this problem with the '84 until I took the other fuel pump out of the '86. That pump probably has about 40-50,000 miles on it. I went ahead and ordered another pump and it should be in tomorrow morning. Am I on the right track here? I seem to recall seeing similar stuff happening to other cars on here. Does this seem like a decent life span for an after market fuel pump (probably an Airtex, from O'Reilly's)? I'm going to change out the filter as well - the car seems to run well otherwise, although lately it has been a lot harder to start. FWIW, the last time I had a fuel pump go bad, it kind of went all the way bad, i.e. car stalled any time I went uphill or got on an incline. Do these pumps go intermittent or have weak diaphragms over time? And how would the heat affect it like this? It seems almost as if air is being pulled into the gas line because of the way it stalls and hiccups... Suggestions are always welcome!

Thanks, Rob

[Petros]

sounds like a heat soak issue causing vapor lock. Mine does the same thing when hot, though not as severe (and of course it does not get quite as hot in the Puget Sound area as it would in North Carolina). A higher pressure pump might help. virtually all the newer EFI cars have eliminated this issue. I suspect that when the car sits, engine off, after running hard, part of the fuel vaporizes in either the carb or the fuel lines since there is not fresh (cooler) fuel being pumped into the lines and carb. It gets hot and vaporizes in a a few places, which the fuel system treats the same as air in the system, and will not run. With a higher pressure pump it will compress the vapor bubbles down to nothing, or very small, so the car will run. The high pressure EFI fuel pumps eliminate this problem since the fuel is under higher pressure and unlikely to vaporize. The problem is the stock float valve in the carb can only take so much pressure before it will leak past the needle valve, flooding the engine and giving poor economy. So there is a limit to how much fuel pressure the carb can take.

Another solution might be to provide better heat insulation for the fuel lines and pump. If you did not install the plastic fuel pump spacer than your fuel pump will transfer more heat into the pump from the head, so you have to reinstall it. It might be possible to make a fuel pump, and carburetor, insulator out of a better insulation material. Make better heat shields for the carb and fuel pump, install a fuel line insulator around all of the exposed fuel lines around the engine to prevent heat transfer into the fuel lines, etc. It might be useful on a really hot day to open your hood when you know you will not be very long, so the heat can escape the engine compartment while it sits. Perhaps rigging a 12v fan to keep cool air circulating under the hood when you park? I would put a timing on that however so you do not run down the battery.

This is another reason I really hate carburetors. The Weber carb can handle even less fuel pressure than the stock carb, so this problem could be even worse with a weber and step-down pressure regulator installed.

Good luck.

[takza]

When I was running and testing heated fuel I had an insulated sensor on the fuel line right before it went into the carb...typically I'd see 100F unheated and around 125F to over 157F with the heat...not regulated too well. I never really had vapor lock...except maybe it took longer to start when the fuel was in the higher range. OEM carb. I'd say a new pump would fix it.

[RiggerRob]

Petros, you pretty much confirmed what I already suspected about fuel vaporizing in the lines. I guess most people with 'modern' cars don't even know what vapor lock really is. My '84 seemed to start and run pretty well before the fuel pump swap (it was unseasonably hot in April when I got this car), so I'm thinking that if the pump is even a little marginal then that's probably the culprit. I'm swapping out for a new one in the morning so we'll see. I do know for a fact that the plastic spacer is in there, which is a good thing because they seem pretty hard to find. Also, I'll try to park it in the shade as much as possible (not always an option), and opening the hood seems like a good idea, as well.

All of this makes me not like carburetors much, either, but it is what it is and it's not a deal breaker for me as long as I don't stall out all of the time. I tend to have a lead foot and it started to stall on me today but I nursed the gas gently and it came back to life. It's almost like the car is reminding me to ease up and be gentle and not treat it like a sports car all the time, You'd think I would have learned my lesson by now...

Just out of curiosity - I've heard of people retrofitting to an electric fuel pump. How well does that really work? And how do you regulate fuel flow with it to keep from flooding the carb every time? I don't want to go in that direction unless this becomes an ongoing issue but it would be good to know if anyone's had any success with it.

[ARCHINSTL]

RiggerRob -
While apparently not related to your prob (you have a fresh tank of fuel), give a look to http://www.tercel4wd.com/forums/viewtop ... f=2&t=5615.
Tom M.

[RiggerRob]

Good one, Arch! I'm learning more and more about the foibles and perils of having an old carburetor equipped vehicle. Could lengthening/wrapping foil around my lines do the trick? For that matter, I've never completely emptied the tank out on mine (although I've come close); could a flush and a fresh refill help out with this? What about fuel stabilizer, what's the best one? At any rate, I'll have a new fuel pump and fuel filter in by tomorrow morning and hopefully some of the issues will resolve themselves. Thanks for everyone's wisdom and feedback on this!

[terc4wdclt]

im having the exact same problem with mine i just bought it yesterday the guy bought it from just change the fuel pump and clean out the gas tank. im not a mechanic but i am mechanically inclined when i have good instruction how hard is it to change the fuel pump on these cars

[RiggerRob]

Fuel pump swap is super easy, remove two top hoses, two bolts in the side, slide it out and swap. I'd definitely recommend removing the air cleaner assembly to get better access to everything. Make sure to put the plastic spacer back in place.

[Petros]

it might be worth a little fuel pressure test before and after the new pump. That is if you have a pressure gauge, but it is easy to do; put the pressure gauge line on the pump output, crank the engine and observe the pressure.

Wrapping the fuel lines loosely with foil is an excellent way to insulate the fuel lines, cheap and easy, though likely not very durable.

You can use a higher pressure fuel pump on this car as long as you install a pressure regulator right before the carb, that way all of the lines have higher fuel pressure, but the needle valve in the carb will see the correct pressure.

the "winter" formulation of gasoline is another issue that modern regulations seem to ignore that older cars use still use carburetors, with high pressure fuel injection there is not likely to much of an issue using winter fuel formulations in warmer weather.

[splatterdog]

Did you use an aftermarket pump spacer? Only use OE as it has a heat shield molded into it that cups the bottom of the pump. The ones that come with replacement pumps do not.

[ARCHINSTL]

As splatterdog recommends...
Rock Auto shows 9 left at a closeout of $7.50. Since it is a Beck-Arnley Part # 0392021, I'd imagine any store could order it. Although cheaper to just go to a JY and remove it from any 3AC or 4AC.
Tom M.

[takza]

You could also wrap the pump in several layers of alum foil.

[splatterdog]

You could also wrap the pump in several layers of alum foil.

Won't that cut into your hat material?

Sorry coudn't resist.....

[Petros]

That way the aliens can't read your car's mind...

[takza]

I wear a REALLY BIG alum foil hat...no problemo.

Have a look at this?

http://www.youtube.com/watch?v=YFB37WLa ... re=related

Sugar cube anyone?

http://www.youtube.com/watch?v=a--3q4fO ... re=related