New FC fuel pump. New problems
11-27-15, 01:41 AM
#1
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New FC fuel pump. New problems
1988 rx7 NA VERT
OK before the new fuel pump the car would rev freely all the way to redline. except for the slight hesitation at around 3800 rpm then it would continue freely to redline. After about thirty for forty minutes of driving it would stall and would no longer want to start till about after an hour. So i replaced the fuel pump. Now itll hesitate and sometimes it feels like it hit a wall. no matter where i have my foot on the throttle it wont go. it gets worse and worse the longer i drive it.
for example ill wait for it to get to operating temp then ill go out and drive it to redline just fine.
drive for another minute or so then try to redline and itll stop at about 6k then keep going.
eventually itll drop down to 4k and then 3k
I first found this problem when i took it for an hour long test drive after the fuelpump installation. i was driving it normally, shifting at about 3k
however on the way back form that trip, i tried redlining and it would not go past 3. i was really confused, so i slowed down went to first. tried to red line that and it wuold go up to 4k before it would cut off. 2nd cuts off at about 3500 3rd cuts off at about 3k.
If anyone would have any idea please help me im a noob.
can it just be that the fuel pump is the problem?
OK before the new fuel pump the car would rev freely all the way to redline. except for the slight hesitation at around 3800 rpm then it would continue freely to redline. After about thirty for forty minutes of driving it would stall and would no longer want to start till about after an hour. So i replaced the fuel pump. Now itll hesitate and sometimes it feels like it hit a wall. no matter where i have my foot on the throttle it wont go. it gets worse and worse the longer i drive it.
for example ill wait for it to get to operating temp then ill go out and drive it to redline just fine.
drive for another minute or so then try to redline and itll stop at about 6k then keep going.
eventually itll drop down to 4k and then 3k
I first found this problem when i took it for an hour long test drive after the fuelpump installation. i was driving it normally, shifting at about 3k
however on the way back form that trip, i tried redlining and it would not go past 3. i was really confused, so i slowed down went to first. tried to red line that and it wuold go up to 4k before it would cut off. 2nd cuts off at about 3500 3rd cuts off at about 3k.
If anyone would have any idea please help me im a noob.
can it just be that the fuel pump is the problem?
Last edited by OuroborosXIV; 11-27-15 at 01:51 AM. Reason: forgot to add car description
11-27-15, 12:16 PM
#3
I'd go back to the old pump and see if the symptoms change back to before. Then I would check system and pump pressure. System is checked with the gauge teed in. Pump pressure is checked with gauge at end of supply hose. There is also the check to see how fast the pressure goes down and maybe another I may be forgetting. See FSM.
Two of the first rules I wish I was told as a noob: 1. Don't throw parts at it - diagnose thoroughly. 2. Always have the FSM and study it. Ours has a troubleshooting section.
Btw, did you get the correct pump? Might as well check pressures while the new one is in, before swapping back and following the first paragraph.
Lastly, I would check the spark plugs for signs of the mixture.
Oh, and post above is easy to follow. Just replace with a test pipe. Maybe someone in your area has one.
Two of the first rules I wish I was told as a noob: 1. Don't throw parts at it - diagnose thoroughly. 2. Always have the FSM and study it. Ours has a troubleshooting section.
Btw, did you get the correct pump? Might as well check pressures while the new one is in, before swapping back and following the first paragraph.
Lastly, I would check the spark plugs for signs of the mixture.
Oh, and post above is easy to follow. Just replace with a test pipe. Maybe someone in your area has one.
Last edited by pfsantos; 11-27-15 at 12:21 PM.
11-28-15, 07:55 PM
#6
You mentioned in your first post that you had a hesitation at 3800 RPM when revving. That is when the secondary injectors kick on. It is common for ground issues to cause the issue you are describing. It is possible that when you disturbed the pump that you may have disturbed a ground. Now, the car ran ok enough until it was hot. Now it seems to run like hot garbage, so I would follow this link to Arron Cake's website where he has a write up on common RX-7 issues caused by grounds.
Proper RX-7 Grounding Procedures
There may be deeper problems, but I personally do not think that the pump was your issue in the first place at all. It's possible that it had a contributing factor, but there is a simple axiom to live by when troubleshooting any problem.
Perform a fix and select one of three outcomes:
1) Nothing is different. You just did something and nothing has changed.
2) It's worse. Oh my god! What did you do! Was there an underlying problem, or did the "fix" unmask something else (ie new sensor now reads good, but another sensor is faulty)
3) It's fixed! Hooray, now crack open a beer and celebrate.
Proper RX-7 Grounding Procedures
There may be deeper problems, but I personally do not think that the pump was your issue in the first place at all. It's possible that it had a contributing factor, but there is a simple axiom to live by when troubleshooting any problem.
Perform a fix and select one of three outcomes:
1) Nothing is different. You just did something and nothing has changed.
2) It's worse. Oh my god! What did you do! Was there an underlying problem, or did the "fix" unmask something else (ie new sensor now reads good, but another sensor is faulty)
3) It's fixed! Hooray, now crack open a beer and celebrate.
11-30-15, 04:02 PM
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Ok so here's what's happening. I'll post a video of the problem when I get home. Anyways just now I was driving from school and then it wouldn't go past 2000. So something fishy is going on. I did see a bunch of **** in the gas tank. So could that he clogging it up? I mean at times when its cool it'll rev up to redline but it'll hesitate kind of like a ground problem. But the other times feels like a rev limiter I hold the gas pedal down and nothing it's like it dies out and once I let the pedal off the rpms drop and then I can step on it again but same thing happens. One more thing it's also been in a fire before so po redid engine bay harness and theres a vacuum leak
Last edited by OuroborosXIV; 11-30-15 at 04:06 PM.
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11-30-15, 05:53 PM
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Sorry for the shitty filming and the sun was in the way. but yea thats what happens. idk if im crazy or this happens more when the car is warmer and when it gets warm it happens when i step on the gas more than about 30% while under load.
11-30-15, 06:12 PM
#13
No that would not be necessary as you're focusing just on the converter. You could also temporarily remove the oxygen sensor and see if it clears things up some as doing so gives the exhaust a path to escape before going to the converter. And perhaps you should also test the water thermosensor to see if it reads properly or not. To do so read the Green/White wire at the ECU at pin 2I. W/key to on the reading should be between 2 to 3 volts w/the engine cold and close to .5 volts fully warmed (sensor helps dictate amount of fuel injected into the engine).
11-30-15, 07:19 PM
#15
2-3, depends. you might actually have 0 if you aren't sure.
however it doesn't sound constipated to me, but still worth a look under there anyways.
the desert kills fuel tanks, so if this is a car you are bringing back to life, yes the junk in the tank may have killed the new pump already. did you drain it completely and put fresh gas in? how long had the car been sitting before you tried to start it?
however it doesn't sound constipated to me, but still worth a look under there anyways.
the desert kills fuel tanks, so if this is a car you are bringing back to life, yes the junk in the tank may have killed the new pump already. did you drain it completely and put fresh gas in? how long had the car been sitting before you tried to start it?
Last edited by RotaryEvolution; 11-30-15 at 07:21 PM.
11-30-15, 09:18 PM
#16
I'm concerned that you said it was in a fire. Anything is possible with a janked harness. Just pull the O2 sensor first and drive it. It takes about 10 minutes and doesnt require you to drop the whole crusty exhaust. At least that way you can eliminate one cause. It does sound like the car is starving for fuel to me, though. Like a bad AFM or even a really bad ignition breakup. The CAS is suceptible to noise, so bad wiring can cause your mess too. Also, check your grounds. A wise man once told me: demons rise up from the GROUND!
11-30-15, 10:17 PM
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Ive actually been driving the car for a few months, it was running fine untill i got the tank completely empty (fuel gauge doesn't work)and i tried starting it a few times. like 20 times to be exact. Then i filled it up an the car started dying out when i drove it over 30 minutes. so i switched out the pump and thats where im at now
11-30-15, 11:01 PM
#18
12-01-15, 10:27 PM
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i changed the fuel filter thats by the wheel well. i didnt know there was two?. And just today things got even more weird. Now when the car is up to temp it wont go past 2k rpm and if i shut it off and start it again itll continue for a few moments before going back to not wanting to pass 2k rpms
12-03-15, 08:37 AM
#20
If this happened after you ran low on fuel, you may have sucked some garbage into the lines and possibly the injectors. Was the filter clogged when you pulled it out? Try blowing through it. There should be no resistance to blowing through it.
Have you gone through and checked all of your grounds yet? Have you verified that you have adequate fuel pressure? Do you know what the voltage is at the pump while running?
I have seen problems with the main efi relay where they fail hot. Cycling the key reestablishes contact, but then high resistance in the contacts starts to cause issues. The relay is the one behind the driver strut tower. Gold colored with two plugs coming out of it.
Have you gone through and checked all of your grounds yet? Have you verified that you have adequate fuel pressure? Do you know what the voltage is at the pump while running?
I have seen problems with the main efi relay where they fail hot. Cycling the key reestablishes contact, but then high resistance in the contacts starts to cause issues. The relay is the one behind the driver strut tower. Gold colored with two plugs coming out of it.
12-04-15, 08:28 PM
#24
Smells like 2 stroke.
Is it possible that you accidentally have pressure and return fuel lines swapped at the fuel tank? I have *almost* done this on two occasions, and I've heard that it will cause the car to run very poorly (if at all.)