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85 GS - Fuel Issues

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Old 12-09-19, 08:35 PM
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85 GS - Fuel Issues

Really excited - picked up another FB. Found a Tender Blue Metallic 85 GS with 80K miles. Didn't need it but I can use some of the body parts on my GSL-SE. Once I bought It I decided it may be in too good shape to cannibalize. I may get tossed off this forum if I steal parts from it.

Body is in great shape, no rust. Interior is very nice. Engine very clean. Even the stock stereo and electric antenna work! Docs suggest car had been sitting for 10+ years (sounds like my 85 GSL-SE). Not much history on why the car was parked but it has fuel issues. Car starts, runs very rich (can smell it), and it idles pretty well but better when cold. Once the accelerator is pressed it starts to die. The guy I bought it from suspected the "secondaries" in the carburetor had issues. Supposedly he had the fuel tank cleaned (ultrasonic) and coated, new fuel pump (aftermarket) and new fuel filters. He also had the carburetor cleaned. Not sure how careful he was with what was obviously a rusty tank to begin with.

At this point not sure if carb needs to be replaced or what. Have started reading through the FSM for ideas. Will start with the basics to include re-check filters, fuel pressure, fuel flow, good ignition, idle. If these symptoms ring a bell please weigh in with suggestions.



Last edited by jkmcafee; 12-09-19 at 08:39 PM.
Old 12-09-19, 09:40 PM
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How's the level of fuel in the bowls of the carb? You can see the fuel level in the little sight glass windows in the sides of the carb.

Old 12-10-19, 03:47 AM
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Glad to hear that he removed the fuel tank and had it professionally cleaned and sealed. This is huge. Inspect and replace the fuel filter if you find sediment ad it could be collecting any residual sediment. You will also want to rebuild the carburetor. The carburetor likely has sediment in the float bowls that's rising as the engine is running and getting sucked into and clogging the jets. A simple cleaning cannot ensure that every air bleed passage is free and that the float bowls are free of sediment.

It is a beautiful example for sure. It's a car I would 5spd swap and enjoy for a long time. Its beautiful! Do you know any of the car's history?
Old 12-11-19, 12:28 PM
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Not much detail about history. Owner provided document that suggests 2nd owner parked it about 12 years ago, so it's been garaged ever since. Young gentleman I bought it from tried to bring it back to life but ran out of resources. I truly bought it for the parts but am having second thoughts.

Replacing the auto for a 5 speed sounds like a really good idea. Not sure what differences there are - maybe carb, starter, etc. Also not sure how it may affect desirability/resale value.

We'll see what happens once I get it running. Any recommendations for someone I may be able to use to rebuild the carb?
Old 12-11-19, 12:30 PM
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Originally Posted by Qingdao
How's the level of fuel in the bowls of the carb? You can see the fuel level in the little sight glass windows in the sides of the carb.
Not sure - I will need to check.
Old 12-11-19, 10:12 PM
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Originally Posted by jkmcafee
Not much detail about history. Owner provided document that suggests 2nd owner parked it about 12 years ago, so it's been garaged ever since. Young gentleman I bought it from tried to bring it back to life but ran out of resources. I truly bought it for the parts but am having second thoughts.

Replacing the auto for a 5 speed sounds like a really good idea. Not sure what differences there are - maybe carb, starter, etc. Also not sure how it may affect desirability/resale value.We'll see what happens once I get it running. Any recommendations for someone I may be able to use to rebuild the carb?
I am not the one for keeping "resale value"; I believe in NOT keeping the …. tight for the next guy if you know what I mean. Swap it over all you need is a tranny, peddles, master and slave clutch and a short hard line for the clutch hydraulics.

If I were to guess I'd say your carb was already rebuild like the po mentioned. But it was rebuilt with new needles and seats. The new needles and seats are binding and causing a flooded condition. I'm sure there are 4 or 5 other forum members that are chomping at the bit waiting to respond in agreeance. If I were you I'd take that top off the carb and remove the needles and seats. Buff them up a little bit to get the rough edges off and re-install them.
Old 12-12-19, 07:09 AM
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".... guy I bought it from suspected the "secondaries" in the carburetor had issues. Supposedly he had the fuel tank cleaned (ultrasonic) and coated, new fuel pump (aftermarket) and new fuel filters. He also had the carburetor cleaned. Not sure how careful he was with what was obviously a rusty tank to begin with."

Fuel tank cleaned, but it has sat for 12 years? Gas still would have gone bad , very bad if it sat for 12 years. Hell the fuel tank probably needs to be cleaned again.

"Once the accelerator is pressed it starts to die. The guy I bought it from suspected the "secondaries" in the carburetor had issues. "

those secondaries open under extreme manifold pressure. I.e when you floor it.

Car sure looks Concours Car Show good! Let us know what the solution is.
Old 12-13-19, 08:14 PM
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Originally Posted by Qingdao
I am not the one for keeping "resale value"; I believe in NOT keeping the …. tight for the next guy if you know what I mean. Swap it over all you need is a tranny, peddles, master and slave clutch and a short hard line for the clutch hydraulics.

If I were to guess I'd say your carb was already rebuild like the po mentioned. But it was rebuilt with new needles and seats. The new needles and seats are binding and causing a flooded condition. I'm sure there are 4 or 5 other forum members that are chomping at the bit waiting to respond in agreeance. If I were you I'd take that top off the carb and remove the needles and seats. Buff them up a little bit to get the rough edges off and re-install them.
No, the previous owner did not rebuild the carb.
Old 12-13-19, 08:16 PM
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Originally Posted by midnight mechanic
".... guy I bought it from suspected the "secondaries" in the carburetor had issues. Supposedly he had the fuel tank cleaned (ultrasonic) and coated, new fuel pump (aftermarket) and new fuel filters. He also had the carburetor cleaned. Not sure how careful he was with what was obviously a rusty tank to begin with."

Fuel tank cleaned, but it has sat for 12 years? Gas still would have gone bad , very bad if it sat for 12 years. Hell the fuel tank probably needs to be cleaned again.

"Once the accelerator is pressed it starts to die. The guy I bought it from suspected the "secondaries" in the carburetor had issues. "

those secondaries open under extreme manifold pressure. I.e when you floor it.

Car sure looks Concours Car Show good! Let us know what the solution is.
Cleaned after it sat for 12 yrs. We will keep you posted. I want to send the carb to someone who knows what they're doing rebuilding these things.... any ideas?
Old 12-15-19, 08:32 AM
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Another thing to look into is the aftermarket fuel pump and whatever else the previous owner added that isn't stock.

For some reason, it seems very common for people to want to go an start swapping in aftermarket 'universal' fuel pumps into these cars. A brand new OEM pump is available from any dealer for a very good price and will probably run for another 30 years.

As for the carb, look into some of the documentation on the Nikki rebuild. It is fairly straightforward, see if it is something you are comfortable with.
Old 12-30-19, 10:31 AM
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Good progress over the holidays with the GS. Not completely finished with fuel issues, but it seems that I've identified root cause - tank issues. Here is what I did:

Started by inspecting what previous owner had done. He had installed aftermarket FP with fuel filters between tank and fuel pump, and between fuel cut valve and carb. Tapped each side of both filters onto paper towels. Not much sediment at all. Gave me misleading confidence. Replaced fuel pump with OEM pump and new fuel filter. Bi-passed fuel relay mounted below instrument panel behind steering wheel so I could have fuel flow with just ignition turned on. Performed isolated test by checking fuel pressure (good) and fuel flow (not good, only about 25% of 1.5 qts per min specification) right at the output of the fuel pump while pulling fuel from the tank.



Repeated test by temporarily removing fuel filter. Same result. Repeated test by pulling fuel from a clean gas can and fuel flow was good.




Since it looked like the line back toward the tank or the pickup was stopped up I used compressed air to blow out supply line back toward the tank. Realizing at this point that I had to drop the tank regardless of whatever else I did but I wanted to see what difference it would make. Reinstalled fuel filter and repeated first test. Viola! Got good fuel capacity similar to pulling from gas can.




Moved to engine compartment. Checked return check valve (good) and blew out return line and supply line back toward fuel pump (still disconnected). Re-connected all fuel lines from the tank up to the check valve. Retested pressure test (good) and flow test (good).



Re-connected check valve and visually checked fuel flow (good) through the carb. Started car and it idled pretty well. Drove car and had no major issues. Will fine tune later, but need drop and inspect tank before I go much farther because it is obviously a tank issue I'm dealing with. No wasted effort so far, all had to be done. Once I pull the tank and resolve that issue I will remove filter at carb, remove relay bypass and fine tune.

More later.

Last edited by jkmcafee; 12-30-19 at 10:38 AM. Reason: typos
Old 01-08-20, 10:48 AM
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Subbing as I'm curious what you find. For a while I've suspected my tank lines are slightly plugged up but I haven't figured out a good solution to clean and re-seal them or whatever (my tank was recently re-coated and is in fine shape besides perhaps the lines - I don't actually know if the lines are my problem). Not trying to steal the thread, but maybe some of your findings will help me as well.
Old 01-10-20, 02:53 AM
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Originally Posted by Benjamin4456
Subbing as I'm curious what you find. For a while I've suspected my tank lines are slightly plugged up but I haven't figured out a good solution to clean and re-seal them or whatever (my tank was recently re-coated and is in fine shape besides perhaps the lines - I don't actually know if the lines are my problem). Not trying to steal the thread, but maybe some of your findings will help me as well.

Will let you know what I find. Disclaimer: this will be a slow process for me. Cars are in my dad's shop in GA, and I'm in FL. But hope to get back some time this month to continue root cause diagnosis.
Old 01-11-20, 05:45 AM
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Glad things are working out for you. Seems like you have the issue narrowed down. Dropping the tank and having it checked and cleaned can't hurt. At least if you remove it and pull the pickup assembly off and look inside of the tank you will know exactly what you're dealing with.
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