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Where is the fuel pump Relay on 92 Chevrolet Caprice (sedan)


Tinman, What exactly is the

Tinman,

What exactly is the problem?
How was it determined that the relay is at fault?

A fuse is gonna blow before the relay, so check for blown fuses. The relay is on the right hand inner fender, inside a little black plastic box marked relays/fuses, with an output of 5 or 6 wires.

It has not yet been

It has not yet been determined that relay is the problem. Haven't got to anything yet; towed back last night. Would not start after 30 mile trip (sudden failure after shut off). The relay is on (near) passenger side firewall/fender; there are two. One is A/C, other is fuel. I'll have to figure out which is which. Still could be anything; coil, fuel pump, relay, pressure switch if there is one. At first, it would almost start, then die immediately. After multiple cranks, it quit doing even that, like it ran out of residual fuel in line. I'm going to look at it tonight. If a fuse went, it would be absolute. Anything else can be intermittent, but suppose even a dribble of fuel could come out initially with no fuel pump. I'll probably check for spark first, then for fuel output on the line somewhere with key on. I just dread it if it's the pump.

Tinman, You failed to post an

Tinman,

You failed to post an engine size. In this case it doesn't matter because the 4.3, 5.0, and 5.7 all use a timing chain and not a timing belt. For the problem you are describing, you have to go back to the basics (below).

Is fuel reaching all the plugs?
Is spark reaching all the plugs?
Are all the injectors firing?
Is there adequate cylinder compression?
Is there an excessive back-pressure problem?
Are any error codes set?
Has the timing belt stretched and jumped time?

If all the above check out, and there is still a no start, then let us know.

Big Block His next post

Big Block

His next post killed me.

Wouldn't the fuel pump relay

Wouldn't the fuel pump relay only energize that year make and model for two seconds and from there the oil pressure fail safe take over?

It's a 5.0 with TBI. Well,

It's a 5.0 with TBI. Well, engine would run on a lot less than 8 cylinders, so I don't care if either fuel or spark are reaching ALL cylinders. It has TBI anyway. Even if it had injectors, they would have had to fail all at one time, wouldn't they? And you just said yourself that it has timing chain and not belt, so I don't have to worry if it jumped time. If it had done that, it probably would have been making a lot of noise. Remember, I said this happened suddenly, after running perfectly fine and then shut off. I don't care about back pressure or cylinder compression either. Most all that stuff would be a waste of time to check because it's not going to happen suddenly. When you have a no start, you are either not getting ANY fuel, or you are not getting ANY spark. None of that other stuff would keep it from firing.
One thing it could be is a combination of BOTH oil pressure sending unit and some fuel delivery element; relay, pump, or cut-out switch if there is one. The oil pressure gauge has been acting up lately. Could be coil too. I've had coils fail on both my other vehicles in the last year. I'll find out soon enough once I start looking at it.

I see you got it fixed which

I see you got it fixed which is good. It seemed you were a little irritated with Big Block 409 and I'm not trying to make it worse but number one it does have injectors. That would be the I in TBI. Number two yes it would usually make some racket but timing chains do jump. You are the one that came here for help not him. If you knew it all it's likely you wouldn't have come here. Maybe you were just testing our skills but I doubt it.

frist you have to find out

frist you have to find out what you'r missing, fuel or spark and take it from there.
check spark at plug and power/ground at the fuel pump connector" if you donn't have a gauge ".

It's definitely the fuel

It's definitely the fuel pump. I had tried as suggested elsewhere banging on the tank with a rubber mallet, but didn't work. I tried it again, and used the pump "test" wire and the pump ran. Couple of times, then wouldn't run and banging didn't work. Resistance on hot pump wire is high again, basically open. I'll replace the pump, strainer, fuel filter, and oil pressure sending unit as I already know it is acting up.
I already had checked spark. Good blue spark. Plus, it fired with a shot of ether. So then I knew it was fuel. By the way, for others' interest, I previously tried propane and did not get a single burp. Don't know if it wasn't enough, or too much, but it didn't work. I've used propane before on small engines, but only to enrichen mixture. Probably was not enough by itself. Was only using a torch.
Thanks for help.

Tin, Glad you got if figured

Tin,

Glad you got if figured out and happy to help man.

I previously tried propane and did not get a single burp.

Watch it with the propane buddy. Best if you don't use it again. Eyes you save could be your own.

It was indeed the fuel pump.

It was indeed the fuel pump. Replaced it (UGH) along with the other stuff, put it all back together, primed it with the test connection, and it fired right up. Probably saved myself a couple hundred bucks at least, and lost a few pounds to boot!

As far as propane goes, gasoline is just as dangerous, if not more so (in its general use). As with all things in life, there is usually a common sense approach to being safe with anything. Unfortunately, common sense seems to have gone the way of the Do-do bird (extinct).

Tinman, The first thing is

Tinman,

The first thing is I'm glad you got it figured out and that we were able to help. The next thing is you made the statements that are showin below.

It was indeed the fuel pump.

As far as propane goes, gasoline is just as dangerous,

Look man, Gas or propane doesn't make a shit bit of difference. Whoever said (and where is it posted) that propane is any safer than gas? Next time you think you may have a failed fuel pump problem, drop us a line first, and we'll post a few different diagnostic checks.

good Job.

good Job.

Fantastic job.

Fantastic job.

If you ever need anymore

If you ever need anymore help, let us know.


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