build thread for 2.8 carb to chevy tbi.

[cammeddrz]

Went electrical, mounted it within 16" of the tank

been there, done that. inside of 3 months that pump will fail.......
and mine was 6" from the tank, the shortest I could make it with a filter in front of it.

worse yet, it started drawing so much power that the fuel pump driver in the ECM burned out.

4 fuel pumps, and an ECM in 1 year is where I am coming from here

She runs great and starts right up, but Bogs down when she gets warmed up.

you know, this is exactly what my fuel pump did, remember rico that horrible sunday afternoon we drove to your shop, and kept having to pull over every 5-10 minutes and let it cool down before we could go again? pretty much the pump was working so hard (they aren't designed to "suck") it would heat up, and lose its ability to keep up. after that day, it was the final straw, I reconfigured the pump to be gravity fed, and have had the exact same pump for 3 years now.

my suggestion for testing if this is what is happening to you, is when the truck is ice-cold go out and hot-wire the pump so it runs continuously for 20 minutes or so without the engine running. then start it and see if it acts all boggy when the engine is cold.

next I would disconnect the o2 sensor and see if that solves anything. you are using the GM ECT sensor right?

 

[Lil-Pony]

well she starts up idles beautifully and then once she reaches operating temp she goes in to a looping idle till she dies, the pump instructions says that its supposed to receive voltage all the time since it a mechanical pump replacement which runs all the time.

 

[cammeddrz]

the pump instructions says that its supposed to receive voltage all the time since it a mechanical pump replacement which runs all the time.

yes the pump would get continuous voltage, that's not what causes them to heat up. its the fact that the pump is trying to "suck" fuel up the pickup tube, which causes them to strain

for example, a person could walk continuously for miles without breaking a sweat. but if they had a load they were pulling, even half a mile and they would be pouring sweat

like I said run the pump without the engine running and see if it starts running weird when the engine is cold

then disconnect the o2 sensor and see if that changes it, often you can change to a 2/3 wire sensor which has a heater in it, which helps with weird issues like these

then disconnect the ect sensor and see if that changes it.

one of these three will let you know which direction to take

 

[Lil-Pony]

K will try.

 

[Lil-Pony]

Also when timing the motor, where should the timing mark line up on the crank shaft?
I know that you need to disable the gm spark curve by disconnecting the wire next to the ecm

 

[cammeddrz]

I believe we set the base timing to 12 degrees

 

[alwaysFlOoReD]

Hey cammeddrz, I was thinking about the fuel pump issue where you say the axial flow? pump will burn out trying to suck fuel up out of the tank. Wouldn't the siphon effect negate that? Especially if you mount the pump level with the bottom of the fuel tank. granted there would be a head to overcome the first time you run the pump but after that, as long as there is no leaks, then it shouldn't be an issue anymore.
Sorry for the threadjack,

Richard

 

[dangerranger83]

My pump has been running strong for a year now and others I know on this site have had theirs going good for longer.

Now one thing I did forget to say that I want to do for the pump is that I'm going to put a barb fitting where the filter would go run a small length of house to it then run a clear filter to that then the line to the gas tank so that I don't have to remove the pump off the frame every time I need to change the screw in filter, which is said to do once a year.

Sent from my rooted SPH-D710 using Tapatalk 2

 

[Lil-Pony]

ill touch the pump debate later on since ive already gone electric. are the marks on the crank pully marked in degrees? ive never timed an engine, and i think that i got it timed but i may have retarded it to much, this may be the cause of my issues since i dint wait for the motor to be at operating temp when i set the timing as good as i could.

 

[Lil-Pony]

Well so far she is running like a top, she runs a little rich due to a sticky left fuel injector. And she bogs down on the hwy due to i think the cat starting to clog. Throttle response is amazing. And im finally able to run 70 with out floor boarding her. Im having to replace the master cylinder right now, but ill post a video of her when i can, college has started back up and ive been really busy.

 

[Lil-Pony]

my mechanic friend keeps saying that i need a 9-13psi fuel pump instead of the 90 psi fuel pump, am i wrong in thinking that if the fuel regulator is working properly it doesnt matter what pump you have as long as it supplies enough flow and pressure at wot

 

[dangerranger83]

I know it sounds weird but when my family had an 94 astro van with a 4.3 tbi on it, the fuel pump only put out 13psi.

Someone's less is more. I would look into what pressure the GM pump was putting out, if you already haven't.

90psi is way to much, the Ford pump should only be putting out 44psi.

A vacuum gauge and A/F guage should tell you what the engine wants.

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[Lil-Pony]

Ordered a 17psi Airtex fuel pump E8094 $113.00. should do the job since it was designed for chevy tbi's i think this info should be added to the tech page, along with the info that the nominal fuel pressure is between 9-13 psi, hell the truck starts and runs off of only 5psi but dies the moment you give it gas. Got the master cylinder swapped and the brakes feel better but my vacuum pressure is too low for some reason, the timing light says i'm dead on a 12 btdc. i may have to time it using a vac gauge, i'm first going to solve what's left of the rich issue, which may help the vac issue.

Got a nice 10" Edelbrock Black air filter. and every thing fits perfectly with out the need or a body lift even the chevy oem air cleaner fits, you may want to trim or remove the hood liner though.


Im starting to understand what my mechanic friend was saying about having to high off a pressure pump, in that the tbi wasnt designed for that, then again it isnt designed for a 84 bronco 2 but thats besides the point. even with the flaws as stated, she runs 3 times better and smoother than she did with the old carb.

 

[alwaysFlOoReD]

Good stuff.

 

[RICO9]

I have an in-line pressure gauge on mine and it's showing 11psi. That's with the the stock mechanical pump feeding the high pressure pump.