1993 Suburban with 5.7L EFI problem

[Donald]

Tried to start my Suburban today and it would turn over fine but would not fire at all. Squirted some starting fluid to see if a fuel or ignition problem and it fired for a second, so its a fuel problem. The vehicle has gas and the filter is not that old. Where do I start looking. Is there a fuse for the EFI or fuel pump, etc. This is the older EFI where they just replaced the carb. with an EFI system.

 

[frankiee]

Have someone Listen at the tank for the fuel pump to turn on.
If not, then give the tank a couple of raps with a 2 by 4 (within reason) to see if it turns on.

Also try to "prime" it by turning the key off for 10 secs then on for 10 seconds about 5 times and see if it starts.

Might have to take it in to get the fuel pressure measured.

 

[Donald]

Are there 2 fuel pumps (one in tank and one under the hood)? Do they have fuses or circuit breakers? I assume both are electric? What about the EFI and its controls, does that have a fuse or circuit breaker?

 

[04SpecV]

quote:

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Originally posted by frankiee:
Have someone Listen at the tank for the fuel pump to turn on.
If not, then give the tank a couple of raps with a 2 by 4 (within reason) to see if it turns on.

Also try to "prime" it by turning the key off for 10 secs then on for 10 seconds about 5 times and see if it starts.

Might have to take it in to get the fuel pressure measured.

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Yeah do this first. It seems to be a common problem..

 

[Matt_S]

Check the fuse box or owner's manual for a description of the fuses. You should be able to locate an EFI, fuel, FP (fuel pump), or some similar fuse. I'd check that first. I wouldn't expect an engine like this to have two fuel pumps. If this is the throttle body-type with the single injector at the top, they run on pretty low pressure, similar to a carb. There's probably a single pump in the tank. If you're lucky, they might have provided an access hatch in the back of the truck so you can access the pump without dropping the tank.

 

[Donald]

I assume when I turn the key to ON (not START) the fuel pump will run for 10 seconds or so without the engine running?

 

[Gary Allan]

A few seconds. They aren't too noisy (like old MG's or anything) ..but you should be able to hear it.

You either aren't getting any fuel from the tank ..or your injector isn't getting the pulse to open.

I used to have this thingie that you put inline with the injector plug ..it would flash/blink if you were getting power to the injector. I believe that you can just pull the injector to determin if you have fuel. It's messy but if you don't have gauges

I found this out by accident on my throttle bodies Tempo. Don't smoke while doing this

 

[dave1251]

Hit your gas tank with the palm of your fist fairly hard. Then try and start it if it works its your fuel pump. Had to do the same with a 99 Yukon 5.7 that I had. Fuel pump will put you back around $200.00 for a aftermarket. For OEM will cost you an arm and leg. These figures if you DIY.

 

[Donald]

I had someone turn over engine in 5 second spurts, turning it off in between and I was under car with rubber mallet banging on gas tank. Could not get vehicle to fire. I found the fuse (good) bolted to engine side of firewall along with fuel pump relay. Do the fuel pump relays ever go bad or almost always the fuel pump. I know I can listen for relay, but even if relay clicks, it may not be providing a good contact for current flow.

I am waiting for a fuel injector tester for TBI (to be shipped) so I can see for sure if the fuel pump is broken.

Someone also said if I replace the fuel pump to look at the connector as it may be melted due to high current flow when pump fails.

Draining the fuel tank and dropping it may be the solution, but seems like a pain.

 

[Donald]

Also if I want to listen for (maybe feel for) fuel pump replay to close, does it close when I turn the key to ON or do I need to turn it to start?

 

[brianl703]

It should close when key turned to ON.

If you've found the relay, it might have a diagram on it which will tell you which terminals are the coil and which are the normally-open switch.

Then you can just jumper across it (with a fused jumper wire in case you make an unintentional connection) to see if the fuel pump works.

 

[9c1]

Some GM fuel injected vehicles have a connector on the wire harness in the engine compartment that just lays lose. On some it is red. This is a direct fuel pump feed. Jumper 12v from the battery (please use a fused jumper -- trust me on that advise) to that connector. If you get fuel, the problem is with the fuel pump relay or the oil pressure gauge or fuel pump fuse. Normal feed to the fuel pump goes through the oil pressure gauge so that fuel pump will not run if there is no oil pressure.
Some automotive mass merchandisers (Auto Zone in my part of the country) will loan you tools. They ask for a deposit to cover the cost of the tool, but return your money when you bring back the tool. Get a fuel pressure test kit. There should be a test port on the fuel rail (if you have port injection) that looks like a Shraeder valve. Test for fuel pressure. Some engines in GM vehicles are very sensitive to fuel pressure. It must be right. I'm not sure what yours should be though. Need a manual to look it up.
Terry

 

[Donald]

This year Suburban has TBI fuel injection so one needs a fuel injection test kit special for TBI, and I have one on order, but not yet arrived. I will ask Autozone if they lend it.

 

[Donald]

OK, I finally got a fuel injector test gauge for a TBI and as expected, the pressure is 0. I can feel the fuel pump relay kick in. So time to pull tank and replace fuel pump. So I loosened the 2 tank straps, unscrewed the 3 screws inside the filler flap and the tank feels stuck in place. I hear maybe its stuck in place with undercoating, etc. I have tried placing a small 2x4 between tank seam and truck frame and first banging with hand, then small sledge hammer, yet tank does not seem to move. Any ideas? The Suburban is not on a lift so while I have some clearence, I do not have a lot.

 

[muddawgs]

sounds like its still connected. you can jack the back up and put stands under it should get your some more clearance. now did you unhook the wire harness at the top of the tank and the send/return lines? these maybe towards the front of the tank close to the cross member or in front of it. you may have to pull the hose to the filler off also. those hose's can get hard and are not the most flexible. there maybe another ground also attached to the tank. these tanks do stick and need some help pry bar help. you'll have to wiggle the tank down some while suporting it and then reach up and disconnect the send/return fuel and the electrical. the lines are not long enough to reach the ground. you may as well do the sending unit also while your at it. you can buy them as a kit allready to drop in. dealer gets close to 300 for this assembly but you can find it for much less on the net or possibly locally. its pretty common for the grey or purple wire on the pump/sending unit assembly to burn itself out on these units in the tank for the trucks and the suburbans as the pump ages. which maybe the case on yours. the pump can be tested once out and let sit for a bit by applying a 12v source to just the pump to verify. replace the pump at a minimum anyway and check the wires in the tank. you have to seal around the ring on the assembly once you get it buttoned back up. i've used wax rings for toilets to seal around the ring (on the outside) at the top of the tank afterwards and it works quite well and keeps it from getting rusty/crusty. be careful and have a buddy help you if you can. good luck.

muddawgs

 

[Donald]

I got the tank out, looks like it was stuck in place by the rubber mats in the front and back for vibration. But the PITA is that in unscrewing the gas hoses I snapped off the male end of the steel gas lines from the fuel sender assembly. The male ends should turn freely allowing the rubber gas hoses to unscrew, but I assume they were rusted in place. A mechanic said when things are like that they replace the fuel sender assembly. An auto parts store said I could buy fuel line repair kits and handle it that way, but the the two lines looked rusty enough that I thought I should go for the new assembly. Got it at NAPA, expensive, but at least not a dealer part.

 

[dave1251]

I hope that you never have to this again Donald. IT'S a pain in the *$$ to bad your sender assembly is rusted. I wish you the best of luck in the future.