1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

fuel cut at high rpm

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Old 01-17-04 | 04:46 PM
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fuel cut at high rpm

i took the gsl-se out for the first time yesterday for a ride since i had installed the new engine (used with low miles). it ran great but when i shifted out on second gear at 6000 rpm's, it hesitated like it was starved of fuel. it broke out if when i shifted quickly into fourth. it seems like it was starved for fuel for a sec. also, i do not have a part on the dynamic chamber. it is black and looks to be a one wire connector. kinda looks like the ground wire on an alternator. at any rate, i think it is the atmospheric pressure sender. i do not hav it. the male end is on the dynamic chamber but i do not have the female end. i may be wrong on it being the aps. anyone have any ideas?
Old 01-17-04 | 05:08 PM
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get a new fuel pump
Old 01-17-04 | 05:11 PM
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check your float levels too
Old 01-17-04 | 05:26 PM
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gsl se's are fuel injected buddy, lol
Old 01-17-04 | 05:26 PM
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fuel pump seems to work fine. it just seems to cut out for a second.
wwilliam54: 13B with FI. float level?
Old 01-17-04 | 05:30 PM
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oh yeah
gsl-se

either the pump or the injectors might be dirty
Old 01-17-04 | 05:32 PM
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perhaps i will have the injectors cleaned. but, it does not do it through first and second???
Old 01-17-04 | 05:33 PM
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Originally posted by mazdaverx713b
perhaps i will have the injectors cleaned. but, it does not do it through first and second???
definatly the pump then
Old 01-17-04 | 07:00 PM
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why would it do it in third and not first or second? is it because it has to work a little harder to keep up with the added load? i was thinking vaccume leak or timing off a little.
Old 01-17-04 | 07:02 PM
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Originally posted by mazdaverx713b
why would it do it in third and not first or second? is it because it has to work a little harder to keep up with the added load? i was thinking vaccume leak or timing off a little.
check those

but it takes more fuel the higher the gear becuase the engine has more load on it
Old 01-17-04 | 07:13 PM
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makes sense. is there a way i can run a thourough fuel pressure test? or would a standard test be ok? the engine runs fine, especially when crusing. i'll have to check the timing on tuesday when i get back home to the car.
Old 01-17-04 | 07:26 PM
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get a quart jar and timer
the haynes manual has the proper fill tim in it i belive
Old 01-17-04 | 07:28 PM
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i'll check that out, thanks.
Old 01-17-04 | 07:34 PM
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When is the last time you adjusted your tps?
Old 01-17-04 | 08:31 PM
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i have never adjusted it. what do you think?
Old 01-18-04 | 09:00 AM
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That beggar has caused a lot of probs, kinda makes sense too if I think about it. Its an easy procedure, it WILL make it run better either way (that is if its out of adjustment) Here is this in case you need it. https://www.rx7club.com/showthread.p...ps+for+dummies
Old 01-18-04 | 11:06 AM
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The connector that you describe on your dynamic chamber is for the intake air temperature sending unit. This is a thermocouple that transmits a signal to the ECU to adjust mixture level for the ambient air temperature. There's another one in the Air Flow Meter, by the way.

The Atmospheric Pressure Sensor is located adjacent to the ECU under the passenger floorboard, and sends a signal to the ECU to adjust mixture for increasing altitude, as in driving from the coast to the mountains.

Your description of the 'fuel starvation' at high load conditions may be volume related, so the other posts suggesting that you look at your fuel flow system (other than floats...) are spot on. I would check the following;

1) fuel filter - EFI fuel filter is huge and much more expensive due to high pressure, get the Mazda factory replacement and feel confident that it's in good shape,
2) fuel pump - check this via fuel pressure readings at the fuel rail leads to see if you're getting good pressure. Fuel dump over time is only really helpful on carb engines, IME, because an EFI system is moving a much higher volume of fuel at a much higher pressure - making it hard to accurately gauge flow rate.
3) fuel lines - if you have any leaks anywhere, it may be releasing fuel from the system and dropping pressure.
4) fuel pressure regulator - on the fuel rail at the rear, you'll see the diaphragm activated fuel pressure regulator that reacts to vacuum signal on the 'rats-nest'. If this vacuum connection is bad (bad hose, hole, missing, etc.) then you will not get higher fuel pressure change for increased load conditions <--- Most Likely Cause!

Good luck, and report back, HTH,
Old 01-18-04 | 12:36 PM
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LongDuck, thank you. i will definatly look at what you reccomended. i am kinda new to the egi system so please bear with me on some of my descriptions. if anyone is selling an intake air tep sending unit, i'd be interested as i have none. thank you all for the advice given. i will definatly look into the possible faults and report back.
Old 01-18-04 | 03:02 PM
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When Air Intake Temp units fail or have an open or short most vehicles run rich.

Many computers have predetermined values that they fill in when they doe not get a reading.

If that is the case on the RX7's then it is NOT your "cut out" problem.

The TPS can cause Havoc and it is a good idea to check that TPS voltage with a good quality meter.
Old 01-18-04 | 03:26 PM
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KehoeAutomotive: thank you for the advice. i actually am missing the intake air temp unit. i have the male end of the connector. i need to get the female end that connects to the harness as well as an idle adjust part (i believe). it connects on the right side of the engine bay, near the strut tower. it has a black female connector with a boot and it is next to a green connector. also i remember i am missing a hose that is in the middle of the lower intake, facing the right. i am not sure what it connects to. it is large. possibly 5/8 in size. i am also missing a hose that is on the rear of the airbox. i have no idea what this connects to. please bear in mind i swapped a 13b back into this car. i couldnt have a 12a in a gsl-se.

Last edited by mazdaverx713b; 01-18-04 at 03:30 PM.
Old 01-18-04 | 06:37 PM
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I have three Turbo 13BT motors on the floor. Will any of the parts off it work for you?
Old 01-18-04 | 06:59 PM
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Mine does the exact same thing, i got smaller jets and a bigger fuel pump....of course you got fuel injection so it may be diferent
Old 01-18-04 | 07:06 PM
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Originally posted by KehoeAutomotive
I have three Turbo 13BT motors on the floor. Will any of the parts off it work for you?
to be honest, i am not sure. prob none of the hoses i need. i am not sure.
Old 01-18-04 | 08:51 PM
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[i]I have three Turbo 13BT motors on the floor. Will any of the parts off it work for you? [/B]
One of those 13BT's will work for me.. pm price, condition etc.

Last edited by Steve Shulz; 01-18-04 at 08:53 PM.
Old 01-18-04 | 09:36 PM
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i would say fuel filter. BUt who knows.



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