Totally baffled. Car has a miss/dies when going in reverse.

281pony

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i figured this was my fuel pump failing. the symptoms;

car randomly has a cutout/miss when driving. not really consistant to rpm's or gear/speed specific.

car will either die or nearly die when i go in reverse. car is guaranteed to either die or damn near die when trying to go in reverse onto some ramps.

NOTHING was touched/adjusted. no cel. no codes. new fuel pump, new filter, good gas, car has been dyno tuned. i dont f'ing get it.
 
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2000xp8

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When you changed the pump did you check to make sure the tub was fully locked into place?
As i said in your other post, sounds like the tub broke loose or is letting the fuel out of it when your car leans forward.
It's common with these gas tanks as they get older.
 

281pony

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well now it's another thing. i should have known a ford with an electrical issue would NOT be easy to fix.

the car runs fine now driving straight, backs up onto ramps, those 2 are fine. NOW when i go around a TURN left or right.. the car will be completely NON-responsive to the pedal for 2-4 seconds. then it is like someone turned it back on.
 

281pony

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When you changed the pump did you check to make sure the tub was fully locked into place?
As i said in your other post, sounds like the tub broke loose or is letting the fuel out of it when your car leans forward.
It's common with these gas tanks as they get older.
i took my time. everything was installed right. i've done probably 10 pumps in these ****boxes before. never had an issue.

not to mention, this started before i touched the pump. i hate to say this, cause i had to trade my 03 cobra in from a fuel filter unexplained nightmare. however, the fuel filter was the last thing i "touched" on the car prior to the issues.

it did drive 100% FINE for atleast 1 week prior to this though. not sure if i should laugh, cry or just burn this pos to the ground right now.
 

2000xp8

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i took my time. everything was installed right. i've done probably 10 pumps in these ****boxes before. never had an issue.
Do you even know what i'm talking about?
I didn't accuse you of installing the pump incorrectly.
The tub that the sock from the pump sits in has nothing to do with installation.
It's welded to the bottom on the tank. Some guys call it the baffles.
It breaks loose and the gas gets away from the pump sock briefly during turns and elevations causing fuel starvation and the engine to cut out. Then when the car straightens out and the gas settles the pump starts picking up fuel again and the car starts back up.
 

281pony

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Do you even know what i'm talking about?
I didn't accuse you of installing the pump incorrectly.
The tub that the sock from the pump sits in has nothing to do with installation.
It's welded to the bottom on the tank. Some guys call it the baffles.
It breaks loose and the gas gets away from the pump sock briefly during turns and elevations causing fuel starvation and the engine to cut out. Then when the car straightens out and the gas settles the pump starts picking up fuel again and the car starts back up.
yes i figured what you meant by the tub. it is solid in the bottom of the tank. gas is staying in the pocket down there, the pump is positioned properly down there.

the car is doing all this with 1/2 tank also. doesnt even need to be a really aggressive turn. it just completely goes limp.
 

jrichker

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If you are certain that the baffle is solidly fixed in place, the next thing is to look at the electrical side of things. The computer monitors the pump power and will set code 95 or 96 if the relay drops power to the pump. Therefore, dump the codes and see if you have code 95 or 96. These two codes do not set the CEL, so they could be present and you would not have any warning.

The problem with the loss of pump power is that codes 95 and 96 only detect loss of pump power at the pump side of the fuel pump relay. It does not actually see if the power wire directly on the pump is getting power.

if you have not already done so, plan on dropping the fuel tank inspect the external wiring pump wiring and ground. Also plan on removing the fuel pump to check the internal wiring and the baffle. Judging from the symptom description, I would place a loose baffle at the top of the suspect list, followed by the inertia switch.

The code 95 and 96 use the same test test path. Code 95 looks for ground problems, while code 96 looks for loss of power problems.

Code 95 causes & tests 91-93 models. –The 95 code is because at one time or another, the fuel pump relay hiccuped and didn't provide power the pump when the computer told it to run. Sometimes this is a one time thing, other times it is a no run or runs poorly condition.

Suspect items are bad fuel pump relay, corrosion in the fuel pump relay socket, inertia switch, wiring damage , corroded connector contacts.

Look for a failing fuel pump relay, bad connections or broken wiring. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. On earlier model cars is under the passenger seat. On Mass Air Conversions, the signal lead that tells the computer that the fuel pump has power may not have been wired correctly. See Mustang Mass Air Conversion | StangNet

Diagram of the fuel pump wiring for 91-93 cars.


Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. No voltage when jumpered, check the fuel pump relay and fuse links.


Power feed: Look for 12 volts at the pink/black wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, or connections. Remember that on 92 or later models the fuel pump relay is located under the Mass Air meter. Watch out for the WOT A/C control relay on these cars, as it is located in the same place and can easily be mistaken for the fuel pump relay.

Relay: Turn on the key and jumper the ECC test connector as previously described. Look for 12 volts at the dark green\yellow wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit.



91-93 Models:
Using the diagram, check the dark green/yellow wire from the fuel pump relay: you should see 12 volts or so. If not the relay has failed or is intermittent. Check the inertia switch: on a hatch it is on the drivers side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Pink/black wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the dark green/yellow wire, swap the relay.
 

281pony

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thank you. i think i just kinda did my own diagnostics that prove the baffles in the tank might be bad. it only does this around right hand turns. gas moves to the drivers side away from pump.

no issues with left hand turns when it pushes to the passenger side.

so i guess ill try to find a gas tank now.. after i run some gas out of this one.

edit; so its not visible to the eye when these baffles go bad? they just don't seal in gas as they should?
 

jrichker

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JB weld epoxy can be used to fix the loose baffle in a tank. You would have to throughly clean the tank & baffle mating surfaces with acetone or MEK prior to applying the JB Weld.
 

281pony

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so if i pick up the tank to drain old gas (my new free tank) and the tub assembly moves at one side. then it is bad? is that correct?

it will rattle back and forth a little bit inside the tank if i shake it. if its sitting flat as it would be in the car, it sits level from what i can tell.. there is the lines that run underneath it. so it doesnt sit completely flush.

maybe im looking at the wrong thing, hell i dont know.
 

281pony

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ok i was looking at the right tub. my old tank had the tub completely broken loose inside. i got the parts swapped to the new tank which has a good baffle.

i am wondering about the tank itself though. its missing the, evap line? i believe provision on the top. my smog and all that is completely removed. is this safe to not have? the tank is from an 87 GT he said. :shrug: i am going to search to see what it really is, the line said evap something on it though. it runs into a hardline that goes up to the front.
 

281pony

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ok did some searching. it should be the evap line then, white plastic fitting. the new tank has this hole either welded or it never had one. looks like original paint over top of it. what threw me off was the hardline, but i guess they can't run a rubber softline from front of car to back huh? :rolleyes:

either way, it just said online it was for pollution control basically. so tank install will go on tonight.

thanks guys, never heard of the baffles coming loose in my years of mustangs. it definately did though. matter of fact when i went to move the tank in my shop, i picked it up with my fingers in the fuel sending unit hole. the baffle came sliding down from the other side of the tank and cut my finger to the bone. good times
 

jrichker

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You may find it necessay to get a vented filler cap to vent the tank. As heat builds up from the gas recciculating, it will pressurize the tank and need to be vented off.

If I remember correctly, the fuel quanity sender access cap had the vent. If necessary, you could swap the access cap between tanks.