webmonk

Hey guys. I'm still in the middle of my search for this answer, but I'm running out of daylight so I was hoping that someone could get me on the fast track so to speak. I've been having loss of power problems since I got this car, and tonight I've been examining the fuel delivery system.

Question: Should the secondaries on the stock carb open when the gas pedal is pushed all the way down with the engine not running? I see the squirts of fuel going to the primaries and their butterflies opening, but the secondaries are just sitting there.

Any ideas?

DBOGGSRX7

The secondaries are vacuum operated, meaning that the car must be running and generating a vacuum in the intake manifold in-order to operate the secondaries. It is also rare for them to open if if the car is running without being under a load.

dennis

DBOGGSRX7

Speaking of which, what is a fair price to pay for a carb at a junk yard?

webmonk

Thanks much for the quick reply. Guess I'm back to looking for vacuum leaks!

Jon

webmonk

Just for fun I tried to get the secondaries to open in the driveway with my girlfriend on the accelerator. Nada, just as Dennis sagely predicted. My next question: How can I test to see if they're opening at all? I certainly don't get the power boost and sound change that I've read about in other posts. (I know that there are more likely other reasons it's not happening.)

Also, any good tutorials on how to track down a vacuum leak or find out what my vacuum pressure numbers are in the first place?

Computers I know. Cars I'm learning.

Rx7carl

About $30 or so.

Need more info on your symptoms. Will it idle at a reasonable rpm? 750 or so? If it does, then you dont got no vacuum leak. Idle vacuum depends on the RPM and the engine health. My fresh engine pulls about 18" at 700, my tired one pulls about 12" at the same rpm.

cdrad51

convert them to mechanical, then drive the car in first to about 4-4.5 k rpm and gradually floor it. Observe what happens. If you don't get anything similar when operating vacuum secondaries, they're not opening.

webmonk

My symptoms are erratic. This is the first RX7 (and first real sportscar) I've ever driven so I don't really have a frame of reference to know what's she's doing right and wrong. I do know that in the nearly two weeks I've had her she's run MUCH better than she is right now, and also much worse. Anyway, I ramble...

She sounds great idling in the driveway (holds right about 700rpm) and revs up and hums nicely when I give it gas. Under load is a different story all together. Low end power is non-existant (I'm not the kind of guy that would do a burnout, but at the moment I couldnt get the tires to break loose if I wanted to.) and high end acceleration is not really there either. Sometimes she studders climbing hills and even on the straightaways.

Here's what I've done so far:
-Changed the plugs and wires.
-Changed the distributor cap and button.
-Oil change.
-New air filter.
-New fuel filter.
-Set the timing back to stock.
-Replaced some of the rougher looking vacuum hoses. (no leaks found)
-Run through 2 tanks of gas with MMO.
-Took the belt off of the AC.
-WD-40 on the linkages and moving parts near the carb.
-Driven about 500 miles.

She ran great for a couple of days and then one morning I started her up and it was back to sluggishness. Any ideas or other simple things for me to check? I've got a muffler from RB on the way and the only other thing I can think of is the fuel pump which I have not tested yet.

BMS2004

my truck mind you its a piston engine would have similar symtoms. ITs always been the old GM carb acting up it might be your floats are just sticking on ya. my guess

DBOGGSRX7

Watch your float bowl levels. what you are describing sounds like fuel starvation, I know that you just replaced your fuel filter, but you may want to take it back off and maybe flush/check it out. Also, check the vacuum hoses you replaced, and make sure you got them back in the right place, specifically around the most forward solinoid valve.

dennis

Rx7carl

Well webmonk, thats a good solid start. One other thing I would suggest (but not related to your problem) is to drain, flush and replace the coolant and check all the hoses carefully, and check/replace the belts. What year is the car? I agree, take a good look at the new fuel filter. Many times you can diagnose a rusty tank by checking the filter often. If it looks dirty already, change it and see if the problem goes away. This could indicate a problem in the tank itself. Not uncommon in old cars like ours. Rust is teh enemy!

Kentetsu

Do you have consistent spark on your primary ignition? I lost mine for a bit and had similar symptoms....Good luck with it!

webmonk

I'm pretty sure I got the hoses off and on properly. The way I did it was take one off and then immediately put the new on in it's place. The problems I'm having did not change after I did the re-hosing.

Spark is good, when it's in the driveway atleast. There a way to check that when driving?

I think I'll take Carl's advice and check the fuel filter again. I've read stories on here where they've gone bad in a matter of days. I guess that would explain the increase in performance followed by a drastic decrease...

Thanks again for all the tips. You guys have turned this forum into a really great resource for people like me. Hopefully, in a few years, I'll be the one handing out advice. ;)

webmonk

Hmm... Just to add one more oddity to this - I just drove her down to buy a new fuel filter. On the way back home I decided she was warm enough to drive hard. Performance was lame and then I heard something I could only describe as a pressure release (like a PFFFFF! sound from behind me) after which the performance immediately increased. She was like a new car all the way home with hard acceleration and the whole bit. That makes me think exhaust blockage, but I'm new to this so I'd value more experienced opinions.

Thanks.

Rx7carl

Could be exhaust blockage. Thats a common problem on original 20+ year old stock exhausts. Also sometimes the fuel vent system gets clogged. The symptoms of this are a big whooshing sound when you remove the gas cap. And driving without the cap cures the problem.

werd

coul be the cats. take them off and look inside them. it will be easy to tell if one is bad or not. also make sure the ignition system is working good. it coulb as simple as new plugs,wires,cap and rotor. i had one where the plug for one of the ignitiors came loose it looks like it is hooked up but it isn't. just some ideas!

webmonk

For now I'm guessing that it's exhaust. She ran like hell all day long with the only side effect being a metal sounding rattle from somewhere in the exhaust system toward the rear. New RB muffler should be here Wed or Thur. We'll see!