4TGTE running issue - for the 3TGTE experts :)

[79GT]

Hey all, as some might already know i am running a 4TGTE (no not a 3T ) in my Ta22 celica.

it was running great at the track day i attended a few months back, but since then (not direectly after), after making no changes to the actual engine itself a issue has shown its face.

initially i thought it was a fuel surging issue as i dont have a surge tank, so i continued to drive it gently until i filled up. then when the tank was on full, a similiar issue was happening.

What i should point out also, my fuel pump, although always noisy, has changed noises (not a constant sound as it used to be). it sounds like it is pulsing almost. now before anyone asks, it is getting 13.5V when the engine is running, so volt drop is not causing the problem.

anyway, back to the problem, if i drive the car gently, ie bellow 3-3500rpm, the engine runs beautifully. however, if i plant my foot through first and then into second, i lose all power like it was being starved of air or fuel, then after losing almost all revs and being thrown from the back to the front of the seat the engine regains power and i can drive normally.

I have been under the impression that it is a fuelling issue mostlikely caused by a dud pump not maintaining fuel pressure in the rail, and a new pump is on its way.

however i was wondering if this is the usual symptom of an engine not having proper fuel pressure....is this likely or could this be one of the pressure switches kicking in, and cutting fuel/spark......or whatever.

also, i should probably add, that i am not running the knock computer at the moment, due mainly to me completely forgetting about it since i removed it when i couldnt get the engine running on initial startup (removing it as an extra thing to be going wrong). (i will be plugging this back in tomoz)

regardless, sorry about the novel, any info or advice/experience with a simliar issue or possible solution would be greatly appreciated.

Cheers all
Jamie

[79GT]

as a side note, i will also say that my oil pressure at running temp & at idle is really quite low, as in abetween 10-20 psi (VERY bottom of my guage) but then at about 3000rpm it shoots up to 60psi. When cold it is running 60psi at idle and up from there with the revs.

i am assuming this is due to both the oil cooler line opening and the oil thining out, but i didnt expect it to be this much of a difference. is this normal...could this have something to do with the issue i am having.

and to through a completely new question into the mix, i find the 4T an incredibly loud engine in comparison to everyother engine i have worked with....are these engine typically noisy or am i missing a crucial piece of fact.
CHeers again guys/gals.

Jamie

[TA22 GT]

Jamie,
I think you should install a fuel pressure gauge and see the pressure is constant, should be around 275kpa.
The 4T GTE is basically identical to the 3T GTE, only difference is the pistons are around 20 thou bigger.

The engine shouldn't be any more noisy than a 3T GTE. If you have no knock sensor it can't be the system retarding the spark.

You need to systematically check everything, start at the fuel pressure, if thats good check the cam and engine timing. I assume you have the stock ECU? If so, have you done anything to the AFM?

I have a fair bit of info on my site about the 3TGTE including wiring diagrams you might find useful.
http://users.chariot.net.au/~stmezz/celica.htm
Cheers,
Simon

[3jcelica]

A cheap way to make a temporary fuel pressure guage is to get one of those cheap compression testers with the bike valve in them (I had a couple laying around), remove the valve, and clamp a T piece onto it. Cheap but I have used mine several times and still works fine.

Roger

[blacktop]

don't they have 2 pressure switches?

I read somewhere that the one before the the throttle body (fuel cut off switch?) should be disabled, as they operate on heavy load causing it to do some of the symptoms you describe.

but I can't be sure, I read it ages ago.

[tomvale13]

How olds teh pump?

Mine started caveatating (sp?) and made different 'surging' noises,

I think its when they start to rust or decay from the inside out?

[turbotoy]

Sounds like air being pumped in along with fuel. I agree with the fuel pressure gauge reply earlier.

[79GT]

thanks for all the responses guys, keep the ideas coming....does anyone know anymore about the pressure switches blacktopspirit spoke of. (i have read about them too, but as i didnt wire this harness up i am not too sure...)

I bought a new pump yesterday, and i am going to fit it over the weekend.
I can drive around off boost, ie gently with no problem. but during this time i would have thought i would have the least demand for fuel and hence any fuel pressure issue that exists would be irrrelevent or undetectable during "gentle" driving...

I will also check all my clamps and hoses, but i dont think there are any obviouse boost leaks.....any good way to test for small ones...

cheers

[blacktop]

not sure if this help with the switches I was talking about

[79GT]

mmm i dont have any of those pressure switches on this motor, however i do have them on a spare motor i have out the back. this being said i dont believe the wiring to this switch was wired into the harness i have, so one would assume whoever wired this harness/modified the stock harness earthed it out when the decided to exclude them.

but hey, we all know what happens when we assume. ass - (of) - u - (&) - me.
if this wire had no feed at all and was simply cut, does anyone know what effect his would have.....

cheers for the pic blacktopspirit

[79GT]

Alright guys, brief update -
i replaced the pump today with a brand new GOSS number. hooked it all up, still making bulk noise, almost the same i would say as the old one. only difference is this pump puts out a constant noise instead of the a pulsing sound like the old one. So now it leaves me wondering what would make the pump so bloody loud.

I messed with the angle a whole bunch (ie holding it in my hand and moving around on all angles and noise remained).
I bypassed my lift pump and ran a hose straight from my fuel line through a glass filter and then into the highpressure pump. still, noise remained.

bellow is a pic from my previous set up, but i am still using that adapter (on the inlet to the fuel pump) to increase the size of the hose. could this be an issue....


i also thought it may have been the pressure regulator on the fuel rail, ie once it opened the first time it didnt close again so the pump was working full ball all the time...i swapped the reg with one off my spare motor and there was no change. so i could assume this was not an issue.....


any other ideas.....cheers guys.

Oh also, i plugged the knock control comp into my harness, although i didnt take it for a drive it did drop my idle from 1000rpm to 500 rpm...is this normal....can i counter this with the idle screw etc or is 500rpm normal for idle....(problem i saw, when i backed off the revs it dropped to 250rpm and sounded like it was about to die but then recovered...)

[turbotoy]

In my experience the only thing that makes pump wine is air being sucked threw the pump. If you have a gas can put the intake side of the pump into it and turn it on. If the problem goes away then you have air. If it doesn't I was wrong. Also an EFI pump likes to push fuel and doesn't suck very well. I would think of moving the pump lower and as close to the tank as possible. I ended up using an efi intank fuel pump from an ae86 to get rid of my howling pump. Hope this helps.

[79GT]

cheers for that turbotoy,

but first to clarify, in the 22's the fuel tank is in the boot and the picture bellow is under the car, so in this case the pump is well bellow the fuel tank, and the only distance between the tank oputlet and the pump, is enough for a filter and tehn the pump, about 25cm of hose.

has anyone used an internal fuel pump with a 22. it must have been done before....but i guess with that you would need baffles and what not.....so prob not worth it with the 22's.

how did the internal fuel pump mod go with yours turbotoy, what car was it in.

cheers, Jamie

[GT1978]

Does the pick up in the TA22 fuel tank have one of those fine mesh filters/screens? If so it might be worth checking if its blocking up.

Glen

[limbo]

just wondering when the last time you changed your fuel filter?
Also have a look at the sparkplugs, may have a faulty plug?