jlc84cam350

Could i possible bypass the fuel pump somehow to a switch, i think i am having some issues with the afm shutting the fuel pump momentarily at 4,000rpm, it does it at various rpms but only when truck is warmed up and a big enough load is put on the engine.

4Crawler

iTrader: (3)

Sure:
- http://www.4crawler.com/4x4/CheapTri...shtml#FuelPump



I had a similar issue one time and it was due to a loose connector at the AFM, a certain frequency engine vibration would jiggle the connector enough to lose contact.

jlc84cam350

its weird, i been trying to figure out this problem all winter long, it only does this when warmed up.

When this does happen, if i keep it WOT, it will just pulse forward, as if it gives off a shot of gas than stops and the cycle starts over i can ususally just shut the ignition off 5 seconds and restart and its as good as new for a a few minutes the the symptoms return.

IT won't do it at quarter throttle, and also "normally" won't do it when engine is still cold.

What sensor would control the injectors? is it also controlled by the afm?

4Crawler

iTrader: (3)

Could be any number of things. Best bet is to just go through all the senders and devices on the engine and test each one per the FSM testing procedure. Basically assume each part is bad and then test it and prove to yourself that it is working OK. If you can't prove it is OK, then that is a likely cause of the problem. Also, pull any stored trouble codes from the ECU, if it is running that bad, there is probably at least one code stored. If there are, note the codes, clear them and then see if they return.

jlc84cam350

even if the check engine is not on or hasn't been on for a long time (2-3 months and that problem was repaired) could it still have codes in it?

4Crawler

iTrader: (3)

You bet, it can have codes stored from the last time the ECU was reset. That is why you usually want to make note the code(s), then clear them and see if they reappear. This is because the code could have been in there from some problem that happened years ago and may have been fixed or has not come back:
- http://www.4crawler.com/4x4/CheapTri...CheckConnector

Bigblock

The last time this happened to me I had to drop the tank(4 runner) and clean the filter on the bottom of the fuel pump.That was 100k ago.

jlc84cam350

thats what im starting to think ill have to do, i have a spare fuel pump that i could swap in at the same time

WOuld probably be easier for me to move the box back instead of removing the tank, the box was already taken off this summer and has new bolts so it shouldnt be seased, i know every single bolt on the gas tank are going to break

snap-on

you could wire a light inline with the fuel pump power so if the power to the pump drops out you would see the light blink off.

but fuel delivery would be likely candidate as it only happens at WOT. (large fuel demand)

start with the frame rail filter first before you move to the intank pump.

jlc84cam350

up to date i have tried
- drainging the gas tank
- changing cap, rotor, spark plug wires,
- fuel filter ( one on the engine block) (22re)
- removed cat
- unplugged o2 sensor
- unplugges temp sensor
- cleaned throttle body
- seafoamed it
- tried testing the afm but i am not sure if i am getting the right reading with ohm meter, not 100% sure how to read it...
- i should also not the engine has aftermarket cam (rv 270 h.o.)
- tried that bypass for fuel pump

I wish i had a buddy that could lend me an AFM so i could try it out but i can only get my hands on a v6 afm.

4Crawler

iTrader: (3)

How to test AFM:
- http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml

How to read an ohm meter:
- http://www.4crawler.com/4x4/CheapTri...oUseAnOhmMeter

scope103

Ahhh .... Perhaps we've found the "problem."

jlc84cam350

i installed this cam 5 years ago when the engine was in my 4runner and ran it for 2 years, it ran fine back then. i just installed that engine in a truck i baught this summer, havent been able to figure out the problem yet.

I will try an do that afm test again with the ohm metter the only part i am not sure about reading is mine i have like 4 different settings i think 2mili ohm, 2ohm, 2k ohm and 20 k ohm. When i chose one say 2k ohm, would that mean the highest reading i could get on the meter would be 2,000 ohms? Say its says 0.458, would this mean a reading of 458 ohms?

4Crawler

iTrader: (3)

Yes, as noted on the page above, the range is the maximum reading on the meter and is is not a "scale factor". So on the 2K scale, you will get readings from 0.000 up to 1.999 corresponding to 0 - 1,999 ohms. So 0.458 = 458 ohms. Some folks think that the "2K" or "2000" is a scale factor such that you take 2000 x 0.458 = 916 oms. But that is not the case, the "scale factor" on the 2K range is basically 1000, so 1000 x 0.458 = 458 ohms.

And as noted on the web page above, often handy to hit up Radio Shack or similar and pick up a few resistors of known values to practice with. So pick up say a 470 ohm resistor and practice with that, you should see something close to a 0.470 reading on the 2K scale. It is easier to know ahead of time what value you should be seeing to know if you are reading things right. Instead if you have an unknown AFM resistance and are unsure whether you are reading the meter right, you'll get a reading, but it is right or not?

Co_94_PU

iTrader: (-1)

It's unlikely but not mentioned. A faulty pressure regulator could be dumping the fuel back to the tank also, there are instructions in the FSM for tesing it.

Since you say it seems related to temperature, I'd wager it's one of the variable resistance (Potentiometer) sensors. Once you get the hang of your multi-meter, test the TPS also.

You say you drained the gas tank, but not if you cleaned the screen or tested the pump or if you found any debris.

scope103

You probably have a 2 megohm scale, which is 2 million ohms full scale (when the meter shows 2.000, it's reading 2 megohms. If it reads 0.066, it's reading 0.066 megohms, which is 66 kilo-ohms or 66,000 ohms.) You probably don't have a 2 ohm scale; the leads all by themselves have around 0.5 to 1 ohm, so any reading on a 2 ohm scale would be off by 50% or more! And you almost certainly don't have a 2 milli-ohm scale; full scale would be 0.002 ohms.

(There are meters that will accurately read well below 2 ohms, but they use a "4-wire" or "Kelvin" connection. Don't worry about it; there's nothing on a truck you can usefully diagnose at those low resistances.)

When you are on the 2k or 20k or 200k scale, the scale is reading correctly but in kilo-ohms. There's no muliplication. 0.453 on the scale is 0.453 kohms. You just need to know that 0.453 kohms is the same as 453 ohms.

jlc84cam350

Everything seems to check out on the afm, i aslo cleaned it up, i will try swapping out the tps with the old engine.

jlc84cam350

ik found that last injector (closesed to firewall) is ticking when it runs, when i unplug that injector the ticking stops, what would this mean?
I think it is still working tho because when i unplug it the engine's idle slows down.

4Crawler

iTrader: (3)

Might mean it is working normally and just making more noise than usual or it might not be working right. FSM has some basic test procedures or send them out for professional cleaning and testing:
- http://www.4crawler.com/4x4/CheapTri...html#Injectors

jlc84cam350

Okay I got some new info,
I swaped out the complete throttle body and tps from the other engine, I cleaned up both tb and plenum as good as I could and although it did not fix my bog problem I found a few horses to my surprise! Very happy I did this lol

On another note, that injector that is ticking maybe still working properly but I think the oring is toast, I spray tb cleaner around it and the engines idle goes up, so I do know I need to fix that...

Next off the I hooked up a test light to the fp and b terminals in the hood just to see something and well, the thing is that the fuel pump does come on with that jumper set up but, it comes off as soon as I hit the starter, then after that the afm takes over and test light shuts down. To me I'm guessing if the afm is shuting off the pump momentarily, that by the time that bypass kicks in when engine is running (if it even is) that the damage is already done and my truck is already bogging, I think I am going to try and find the exact wire that send power to the fuel pump and wire up a light inside the cab like snap-on said