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1970 Road Runner Fuel Delivery Issue

R

RoadRunning

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My Road Runner sat for many years and we finally got it up and running again. It had a few good test runs but the latest test run had the car stuttering to a stop and engine shut down. Looks like it is lack of fuel getting to
the engine. We filled up the fuel tank with about 5 gallons of gas and have not even driven it more than 2 miles so I know it is not out of gas. I even looked in the tank with a flashlight and can see gas.

The fuel filter has some fuel in it but does not appear to be very "active" or bubbly. We pulled the fuel filter and found some debris in it probably from the gas tank sitting. Do you think this problem will keep happening or will I need to completely remove the gas tank and pay someone to overhaul it? Any other thoughts?

This is a photo of what came out of the fuel filter that we have hooked in line next to the carburetor:
IMG_2694.JPG


Thanks in advance!
 
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RoadRunning said:
We filled up the fuel tank with about 5 gallons of oil...
Click to expand...

I assume you meant fuel/gas. I'd say you should start with the tank, given the crap in the picture. The sediment will probably continue to block the pickup in the tank. Send it out to be cleaned and sealed. If it were me I'd replace every fuel line up to the fuel pump with new. Then replace the pump. Then rebuild the carb.

Next check the brakes. Those might be getting gummy after all the years of sitting.
 
rlem1977 said:
I assume you meant fuel/gas. I'd say you should start with the tank, given the crap in the picture. The sediment will probably continue to block the pickup in the tank. Send it out to be cleaned and sealed. If it were me I'd replace every fuel line up to the fuel pump with new. Then replace the pump. Then rebuild the carb.

Next check the brakes. Those might be getting gummy after all the years of sitting.
Click to expand...
Yes you are right on I meant gas, made that edit to the post now.

Hmmm hopefully I can find someone in the area (East Bay Area, CA) to get this work done as we cannot do it ourselves without costing an arm and a leg. Carb is brand new Holley so no need to do anything on that front.
 
It's really not that bad a job to do it yourself. I changed my tank and upgraded to 3/8 line by myself with the car on jack stands. A helper is a big plus though, if you decide to tackle it, give us a shout and we can walk you through it. No way it will cost more money to do it yourself than to pay somebody to do it
 
I had the same issue: crap in the tank. In my case, it was like a fine silt, and enough of it made its way through the fuel filter to screw up my carb with sediment, even after I put double filters on the fuel line.

I would clean or replace your tank. Flush your lines carefully and stop driving it until you know you have clean gas. I found out the hard way and had to rebuild my carb too...

Good luck
 
These guys all are making very good points. However, if you have very little money & are willing to risk your carburetor, the el-cheepo way might be to put a very large magnet (Lowe's Hardware or an old speaker) on the bottom of the fuel tank & carry a couple fuel filters with you. When it starts acting up, just put in a new fuel filter (carry a screwdriver with you).... eventually, the rust will stop. I would also suggest you run a bottle of red Heet in every tank for the next 2-3 tanks of fuel (takes out water & red is 3x better than yellow Heet).

I "think" the stuff in your filter is rust out of the fuel line. I think it's too big to get past the sock in the fuel tank.

Having said all of that stuff.....these other guys are giving you better advice, and even using the el-cheepo method, I would still want to drop the fuel tank and change the fuel pickup sock at least.
 
The fuel pump push rod needs to be examined as well. Even with all new tank, sending unit and lines, if the pump is not working properly, your going to have an issue. As everyone has mentioned, work in distinct areas starting at the fuel tank working to the carb. I would start with examing the fuel tank. Flush it out and examine for corrosion in the fuel that is removed. If you need a tank, go with the better quality tanks. Some of the powder coated tanks will not hold up well and will start rusting internally within a years time.

If your fuel sending unit is not rusted up, clean and reuse as the reproductions seldom work as the originals. Simply replace the pickup filter. After cleaning the tank and checking on the sending unit filter, replace the short rubber lines from the tank to the hard metal lines. A pin hole that will not even leak will result in a fuel delivery issue if it starts sucking air. At that point, I would drop the fuel lines and pour clean fuel into the lines flushing them clean. If it is obstructed, compressed air can sometimes dislodge trash, but you may end up having to replace the lines if they are rusty internally.

With those areas covered, you can then know that your delivery system is clean. A new carb will quickly run poorly if it is getting filled with contaminated fuel. Most all of the work can be done in your drive with regular hand tools and minimum mechanical skills.
 
The other bandaid fix is to put a coarse (125um+) fuel filter at the outlet of the fuel tank and a fine filter (20um) at the inlet to the carb. Napa sells them in metal or plastic. If you just have one fine filter at the carb it will keep plugging. I still use the original tank, the coarse filter at the sending unit really works I've run this setup for a long time.

Of course you cant have 5lbs of rust in there and hope to get by, it will need to be flushed out in that case. Dropping the tank out empty is not hard on jackstands, I use a small jack as an extra pair of hands to strap the tank back in. Always run at least one filter.
 
Dirty tank killed my RR. I run a six pack and had the same problem you are having. I rebuilt all three carbs so many times that I can do it with my eyes closed. My problem was the silt got into the needle and seats and I could not maintain the float level. It would burble at times. When I pulled the hood, you could see that the secondary carbs were soaking wet...one time the fuel was rushing out the float vent. New tanks are not too expensive. If replacing the tank, be sure to get a new sending unit. I'd go with 3/8" in case you want to add power later. As mentioned before, all the hose connections and filters should go in the garbage. Good luck.
 
69bfan said:
The fuel pump push rod needs to be examined as well.
Click to expand...

Absolutely. Here's the one from my daughter's 69 Charger when we pulled it after about 100mi. About 1/4" worn off the cam end. Bottom one is an NOS I found. From what I read, the best option, beyond NOS, is finding a good, used original. There was a run of bad MP repros, plus I hear some of the other aftermarket ones are suspect as well.
sYsylEw.jpg
 
I have had good luck with the Mancini fuel pump pushrods
 
Hi Guys,
Ok, I think I am going to go the safe route and replace the tank. Is it better to replace the tank with one off of yearone.com ($120) or boil out/repair the original tank?
I plan on buying the tank and the sending unit. Will blow out the original fuel lines with air.
Is there anything else I need?
Do I need an insulation pad for the tank? I dont think there is a insulation pad for the 70 road runner?
Do I need any other gaskets or anything?
I have the service manual and plan on doing it myself to save some money, on a scale of 1 to 10 (10 is the hardest), how hard is this job?
Going to have to find a place to put all the potentially bad gas I take out of the tank as it sits now..

Thanks for the feedback!
 
New tank, New sending unit, New sock. Yes, needs pad. Easy job#1, the most important consideration is safe handling of the fuel. I'd get a new neck grommet as well.
 
Buy a spectra tank (shop around for price but buy spectra)
Available new sending units are pretty much crap but if you have to, you have to. (Unless yours is good enough to reuse, buy a lock ring from Bill Rolik, either that or it will leak)
I would replace the pad or use one
Fuel filler neck grommet is a good idea to replace
You need a floor jack, a piece of wood to go between the jack and the tank. A helper is a good idea but I did mine with no help.
Remove the sections of rubber fuel line and the sending unit wire
Support the tank with the jack, remove the nuts from the j bolts and slowly lower the tank. Reverse to reinstall, you should probably replace the j bolts as well. On the reinstall, hook the j bolts first then attach the straps. Buy good j bolts like these from Ehrenburg
https://www.ebay.com/itm/Mopar-OEM-...453771?hash=item4b43b48f0b:g:rLoAAOSwfVpYq0N7
 
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Re use your sending unit locking ring. The new one will leak. Make sure everything is set right with the locking ring, and rubber gasket. Also, drain the tank first. Fuel weighs a ton. As was said, if you can use the original sending unit, do it. The new ones can be inaccurate. Change the filler tube grommet. You might want to change the fuel lines too. They can hold alot of trash. The picture of the crud that was in the bowl is more than enough to make the needle, and seat stick in your carb. Couldn't hurt to remove the float bowl, and hose it out with carb cleaner.
 
Thanks for the feedback. This helps a lot. Looks like this spectra tank https://www.oreillyauto.com/detail/...ctra-premium-19-gallon-fuel-tank/cr9d/4358270 comes with the filler tube grommet and lock ring (but will try to use current lock ring instead).
If I buy that and this pad that comes with sending unit seal set https://www.detroitmuscletechnologi...d-insulation-070-felt-paper-grommet-seal-set/
and also buy a sock filter for current sending unit and reuse that sending unit, I should be good to go? Might need some new J-bolts?
Thanks!
 
Be careful of the cheaper incorrect fuel tank pads. They are more prone to hold moisture against the trunk floor which is one of the reasons that these cars have rusted out trunk pans. We offer an OE level fuel tank pad, but for most, it is overkill. A cheaper alternative is available or you can always take a piece of roofing tar paper and cut one out on the cheap.

Avoid the el cheapo fuel tanks. There is a good chance that it will start to rust internally within two years of service. The Spectra tanks are an OEM supplier and are not that much more than the cheaper tanks. Be forewarned that nobody offers a fuel sending unit current day that operates properly out of the box. Some are more accurate than others. Sp be prepared to do some tweaking. As others have mentioned, the lock ring on all of the reproductions that I am aware of are thinner than the original stampings. We provide the thicker lock rings to various vendors, so be aware of that issue. Also, I assume that your going back to a 5/16" unit as a 3/8" and a 1/2" is available. Just know which style to order so as to get the correct filter.

On the 70 B-Body fuel filler neck grommet, they use an extra rib. You can go with that style or the 67 to 69 B-Body style. I would ask to purchase one made from nitrile as it holds up much better to the gasoline as offered today. The original nuts on the fuel tank nuts used a nylon pellet insert so as not to loosen up after use. After all of these years, many of them are very difficult to remove, so as mentioned above, it may warrant the money for a new set of fuel tank studs. Also, the original fuel tank ground strap was relatively short and can be tricky to get a good ground which is one reason that some people have issues with the sending units. A longer ground strap is available or a good piece of wire can fabricate a good ground source.

As Bill Monk state above, it is not a terribly complex job, just dirty and for most, it involves laying on your back in the drive doing the job. Good luck.
 
I think I will be removing the fuel tank and have it repaired/boiled out and then replace as the original tank. Question: The tank is a California Emissions model where it has the 3 or 4 vent ports coming out the side of the tank. Since this car does not need to be smogged anymore, do you think I can simply cut those Emissions line vents and simply plug those holes in the tank? Or do I need to make sure those Emissions lines are hooked back up correctly for it to run smoothly? Those vent lines are pretty old also so if I kept them I may need to replace them..
 
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