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Troubleshooting New 82 RX7 GSL Fuel Delivery Issue
Hello everyone I recently bought a very clean 82 RX7 GSL that had been sitting covered, garaged, & un-driven for something like 18 years. It was a super good find that was a 1-owner car that had (actually true) ran perfectly when parked.
I drained the gas, filled the tank with a gallon of lacquer thinner, re-draind the tank, cycled old fuel out of lines, and changed the fuel filter. Additionally I changed the diff, trans, oil, and brake fluids. Also I changed the plugs, wires, cap & rotor. After all that the car runs & drives, does not smoke whatsoever.
BUT... there seems to be a fuel delivery issue. It free revs smoothly, but under load it seems to starve for fuel. I made a couple videos of it yesterday and put them on Youtube:
I'm a fairly seasoned wrencher but this is my first carburetor vehicle in my collection. I bought the Hygrade carburetor rebuild kit and am going to tear into it, but I thought first I would see if you guys saw how it was running and had suggestions on what to track down first. I will use one of my propane torches to try and track down a vacuum leak, not sure how a vacuum leak would behave on these.
I'm intent on keeping this car original minus rims/tires & possible suspension work. I do NOT want to hack away at anything or put to track use (got other cars for that), just to give it a good home and do some weekend spirited driving.
Thanks guys and I appreciate your input. I'll attach pics for motivation!
Pull gas tank and look inside,clean,coat whatever it needs. Replace all rubber fuel lines,pump...
Look at windows in front and rear float bowls,fuel level should be 1/2 way up sight glass. Need a mirror to see rear float bowl window. If fuel level is as described,don’t mess with float adjustments. Factory settings are always spot on.
Don’t replace oe needles and seats with those supplied in kit,they’re not machined properly and without a lot of fussing to make them work properly you’ll have carb flooding issues.
Clean carb thoroughly along with all jets and air bleeds and hardware
Listening to your videos sounds as if secondaries in carb are not operational.
May want to look into fan clutch,in your videos it sounds as if fan clutch is locked up and if so is sapping a fair amount of power from engine to turn it. They’re still available from Mazda.
GSLSEforme much appreciated - exactly the types of suggestions I was looking for. I forgot to mention that I tested the FP at the carburetor and it was within spec. I gotta figure that would exclude the tank/pump as potential suspects.
Will definitely look into the fan clutch too. I thought it sounded a bit more engaged immediately on startup than it should be. First thing first is get it running right though. Once again I appreciate the input!
Did you test pump for pressure and volume?
Depending on where vehicle spent it’s dormant time,the fuel tank can have a buildup of gunk that accumulates on pickup in tank while car is being driven that can cause driveability/power issues similar to symptoms you speak of.
Agree, sounds like classic gunked fuel tank, plugging your fuel filter prob every time you try to drive it. Prob not doing the carb any favors either. Mine did the same. Drained and dropped the tank, had rad shop chem/hot tank dunk it to clean it, then applied POR15's Fuel tank cleaner/liner kit to seal up the tank inside. Nice looking RX BTW...
Stu A
80GS
AZ
Last edited by 7aull; 10-27-19 at 12:47 PM.
Reason: spelling
As an aside, it's perfectly normal for the fan clutch to engage fully on startup for about the first 5-15 seconds as the mass of silicone oil is circulated through the vanes and channels. Once the fluid starts to flow internally, the fan clutch disengages and you can hear the "prop noise" drop back considerably. This is one good test to be sure the fan clutch is operating as designed.
Have you removed the fuel tank yet and re.ovef the pickup assembly to see inside of the tank? You will likely have to have the tank boiled out professionally if there is a lot of varnished fuel and sediment in it. Have you removed and inspected the fuel filter since you installed a new one? You may find that it's full of sediment from the tank.
Following that I would suggest rebuilding the carburetor as varnishes gas could be plugging the jets and sediment could have settled in the float bowls.
So update - I got the tank out and yes its full of varnished fuel reminents. I power washed it about 8 times and still seem to get build up every time I let the water drain out. The baffles make it impossible to get everything. Seems l need it professionally cleaned. I'm not seeing any new tank options that aren't universal.
In other troubleshooting I popped the carb out and the secondaries seemed to be gummed up/shut. I sprayed the hell out of it, lubed everything linkage wise and tossed it back on (without rebuilding). The floats fill up halfway as they should.
ALSO, I compression checked it and it is within specs - which was a welcomed site.
PLAN - get tank cleaned, replace filter, fire it up & see....
The amount of time your car sat with fuel in it is causing your current fuel system woes.
Getting tank cleaned at a radiator shop is generally what is done and depending on condition(rust) it may or may not need to be coated.
Consider replacing all fuel line hose as ethanol fuel will have begun to break it down some time ago-it may look ok on the outside.
Also consider purging your undercar steel fiel lines while system is open with brakleen and compressed air.
I’m sure you want to see how car runs after doing all the fuel system work. It’s highly likely the carb needs a thorough cleaning with new gaskets for the car to run properly. There is no reason your car won’t run as new afterwards.
Well I dropped the gas tank off today and in 2 weeks will have it back fully restored. I got lucky with a shop out here that does very thorough work and are reasonable.
Also, will definitely replace the rubber hoses and shoot cleaner/compressed air through the steel lines. I have a feeling as well that in order for it to run 100% it'll mean pulling the carb off one more time to clean it. I'll try it out first though to see how it behaves after the tank.
I'll keep posting once I get everything back & installed. Looking forward to getting it back on the road.
10-26-19, 12:32 PM
