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88mustangman 04-07-2010 12:29 PM

hesitation and popping
i got a 88 mustang 5.0, i sometimes have hesitation and popping sound from under the car when i take off . checked the fuel psi during idle its at 27-28psi, when i take off it goes to about 34-35psi. i run 93 octane and only get about 150 miles to a tank .

mattdel 04-07-2010 01:04 PM

pressure is a bit low but still within an acceptable range, but flow might be a problem.
check fuel filter. then do the testing procedures for the TFI module and pickup coil(PIP).
If that all checks out, drop your tank and look for the broken baffle that is interrupting fuel flow.

88mustangman 04-07-2010 01:20 PM

thanks , i've allready replaced the fuel filter, i'll check the rest.other than this heistation its runs good , i've eliminated the smog pump , rebuilt the motor new clutch and cable , all new exaust no cats with 40 sires flowm. and milage still sucks!

88mustangman 04-07-2010 01:29 PM

also it would not do the hesitation while i had the gage hooked up to it, so i don't know if the psi drops during or not or if it changes alot...any help would be greatful....

mattdel 04-07-2010 02:21 PM

sounds more and more like the baffle will be the issue. it will be intermittent, but likely cause fuel starvation when punching it from a dead stop, and taking hard right hand turns.

g3mustang 04-08-2010 09:15 AM

mattdel to be more clear a baffle in the gas tank??? is it easy to tell if its broken. how do you fix new tank???

mattdel 04-08-2010 11:18 AM


Originally Posted by g3mustang (Post 6931624)
mattdel to be more clear a baffle in the gas tank??? is it easy to tell if its broken. how do you fix new tank???

yah, theres a thin piece of galvanized aluminum that surrounds the fuel pump in a circular fashion, its designed to hold about a half gallon of fuel around the pump on a constant basis, to eliminate fuel flosh(essentially starvation), and to keep the pump cool.

the problem is that the stock tanks were poorly designed, and the baffle is only barely tack welded to the bottom of the tank. after years and years of low fuel levels causing fuel slosh against the baffle, it begins to crack the welds, and eventually it will snap free, giving the fuel opportunity to move completely away from the pump in certain circumstances.

it can cause numerous problems aside from driveability, one of which(in my case) was that it snapped the sending unit(for the gauge) completely in half, thus rendering my gauge useless. it also bent my pickup unit so hard that the sock filter snapped off my pump, and flow was disrupted even more by the pump resting up against the side of the pickup.

the reason it causes starvation issues is because the pump is located to the far right side of the tank, so if you take a hard right hand turn, all your fuel will slosh to the left, and if the baffle isn't there, you starve the pump. Same case with straight line take offs, if your fuel level is low enough, it will starve the pump as all the fuel sloshes to the rear of the tank. It only takes a second of no fuel to the pump to cause a big hiccup in performance, and when the fuel comes back, its like the car springs back to life.

this is a picture of my fuel pickup and pump, after discovering that my baffle had broken loose.

due to the fumes in the tank, regardless of how long you let it dry, the only SAFE way to repair this is with a new tank. Autozone has a line of tanks that is pretty solid, but they do need to be ordered. They're about $100.

mjr46 04-08-2010 11:43 AM

run a koer test and check for codes , make sure it's not a efi management issue

g3mustang 04-08-2010 01:42 PM

thats crazy im changing my pump soon to a 255 b/c im going to run spray... so i will look out for this when i drop my tank

88mustangman 04-08-2010 04:38 PM

i drove around with the fuel gage hooked up and taped to my window for 2 days and finally got the problem to happen while the gage was hooked up . the fuel psi had no change , so its got to be somethin else. i'm gonna goahead and change the TFI mod. and the pickup coil and see how that works but, i can't get the pickup plate to come off or pull out, it only pulls up about 2mm thats it....

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