92 hard to start when hot

[Jerry80871852]

Thanks much for the quick reply and the information sent in the PM, I do appreciate it.

I'm just speculating.

My fuel spider has about 8,000 miles on it, my fuel pump has about 12,000 miles. I would suppose that it should still be good for in this time the engine has never been hot, in fact I bought my 92 Blazer new in 92 and its never overheated, so it has not been exposes to extreme heat nor been abused. One would think with all this having been replaced I would not be having trouble with them this soon. Yet we all know that even new parts can go bad quickly at times.

That said it seems my best move and only move is to get a fuel pressure gauge and make theses checks, them I will know what I'm looking at.

If the pressure regulator on my injector assembly happens to be bad, can I just replace it?

[old_master]

Yes, the regulator can be serviced separately. Run the test and post the results before replacing any parts.

[Jerry80871852]

I ordered the gauge you referred to, received it today, but the gauge is faulty, it fills up with gas and them the gas runs everywhere.

I did do this, of course with the faulty gauge one can't be positive of the results.

Turn on key, pressure goes up, yet quickly falls to zero. I tried this 3 or 4 times, same result.

I did start the engine for a few moments, had to use starting fluid of course, which with fuel gauge as is one can't be sure of accuracy, pressure fluctuated from 50 to 54 pounds. Which I did not let it idle but for maybe 25 to 40 seconds.

I've contacted Harbor Freight, now we will see just how good Harbor Freights customer services is.

So now I'm still playing the waiting game.

[old_master]

Autozone and Advance Auto Parts rent/loan them if you don't want to wait.

[Jerry80871852]

Harbor Freight has a place at Texarkana, TX, a bit over 50 miles away. Today my wife had a doctor appointment down there so I went by their store, exchanged this fuel pump tester with out problems whatsoever. This one works great.

My pressure is low when the engine is cold, about 48 pounds. I turned the key on and off several times, still the pressure was at 48. Of course for it to start properly it has to be 55 or better, so I at least know I've got a problem somewhere in my fuel system.

After I started it using starting fluid, let it warm up, them killed it, the pressure was setting on 62 pounds, and of course it starts great them. Running pressure at idle is about 52-53 Pounds.

I might say after its been started and warmed up it starts OK. I've started it several times now with starting fluid and went to town and have been out of it as long as a couple of hours and it started OK.

I'll have to get me a set up to put in place of my fuel filter in order to finish checking out my system. I think we have a forecast of rain in the next day or 2, if so being as my workshop's roof is the sky, that may hinder this old man.

I meant to say earlier I know that starting fluid can be dangerous and appreciate you mentioning that fact, I drove a truck up through the late 80's until a back injury forced me to stop. I always made sure to have a can of starting fluid with me at all times. It saved my day many times and I've know of many truck drivers that were quite happy that I had a can of it. Old habits are hard to break, I generally always have a can of it around the place, just in case.

And thanks again for your advise on this subject.

[old_master]

When fuel pressure drops below approximately 50psi, there isn't enough pressure to open the poppet valves and they won't squirt fuel. If it starts when adding fluid, that's a classic symptom of low pressure, which you confirmed. After the engine is running, available voltage at the pump increases and that's probably enough to bring fuel pressure above 50psi. If the pressure does not leakdown after the pump shuts off, and the voltage and ground at the pump are OK, the pump needs replacement. If that's the case, fuel pumps are not a place to cut corners, use an AC Delco or Delphi pump.

[Jerry80871852]

Oh boy the fun begins, I just love where they place fuel pumps nowadays. Its such a joy to drop the fuel tank on a Blazer S-10. At least this time I will not have a full fuel tank to deal with. On the last one I had just filled up them drove about 15 miles.

Got one ordered, this time I'm replacing the whole assembly even though it cost several dollars more for since last time my gas gauge has not worked quite right and this will be the third fuel pump.

[Jerry80871852]

Any tips on getting my fuel lines started? In 2005 they were a bit of trouble, but much more now than them. When I get the fuel lines started I'll be headed for home plate.

[Jerry80871852]

New fuel pump fixed part of my trouble. Fuel pressure 60 # when ignition switch turned on and my old blazer starts very good. Appreciate all advice given.

At 1st I thought my fast idle was fixed too. I started it 3 or 4 times, did great, them I let it warm up, idled perfectly.

When on a test run to town & to fill up my gas tank, when I pulled into the convenience store it was back idling quite fast, not so fast that it would be dangerous to drive but yet aggravating. Outside of the fast idle it runs just fine.

I can unplug the lead to the Throttle Position Sensor and it idles down perfectly.

I recently took the IAC valve off and cleaned it up, I did not test it to see if it was operational, I wanted to be sure it was safe to do so before using jumpers on it.

Any advice would be appreciated.

[old_master]

Could be a problem with the throttle position sensor. It's possible for it to indicate too high of voltage but not turn the check engine light on. With the engine at idle, the dark blue wire at the throttle position sensor should show approximately .5VDC Check it and post your results.

[Jerry80871852]

OK, thanks, probably be next week before I can check this. I've got some things to catch up on after fooling with this fuel pump nearly all week.

Changing fuel pumps is not a great job for someone that's had several neck surgeries.

Guess I should have said I do not have no check engine lights burning. Sorry.

[Jerry80871852]

Thought I would mention this, maybe it will help someone.

When I 1st got everything hooked back up I had a big scare. When I turned on the ignition switch my fuel pressure went to + 60 #'s, but quickly dropped to 25 #'s.

I thought, oh no, a bad fuel pump. I turned the switch on and off several times and it did the very same thing. I tried starting it, it cranked right up. I let it run a few minutes, them kill it, fuel pressure drops to 25.

I hit the started, it cranks right up. I'm scratching my head thinking it should not start, there is no way this is right. After about 30 minutes with no change I take a break. During this time I think about my ground wire, I had hooked it up at a different place from where it had been, for it was hard to get to and I had just cut the ground wire when taking the old pump off for here at my age and condition my hands will not work in tight places.

Finally I decided, I going to take the bolt out where my old ground wires was hooked and move the new ground wire to there. With much frustration taking that old bolt out, moving my ground wire, I crawl out from under my blazer and go turn on the key, bingo, 62 #'s of fuel pressure, hit the starter, starts great.

I fail to understand why it did not get a good ground where I 1st hooked it up, yet one thing is clear, for some reason it did not. Sometimes we forget how important the ground wire is and just because it is tightly bolted to a portion of the frame does not mean its grounded good. I'm just glad I thought about it and did not pull the tank back off.

[MT-2500]

Originally Posted by Jerry80871852

Thought I would mention this, maybe it will help someone.

When I 1st got everything hooked back up I had a big scare. When I turned on the ignition switch my fuel pressure went to + 60 #'s, but quickly dropped to 25 #'s.

I thought, oh no, a bad fuel pump. I turned the switch on and off several times and it did the very same thing. I tried starting it, it cranked right up. I let it run a few minutes, them kill it, fuel pressure drops to 25.

I hit the started, it cranks right up. I'm scratching my head thinking it should not start, there is no way this is right. After about 30 minutes with no change I take a break. During this time I think about my ground wire, I had hooked it up at a different place from where it had been, for it was hard to get to and I had just cut the ground wire when taking the old pump off for here at my age and condition my hands will not work in tight places.

Finally I decided, I going to take the bolt out where my old ground wires was hooked and move the new ground wire to there. With much frustration taking that old bolt out, moving my ground wire, I crawl out from under my blazer and go turn on the key, bingo, 62 #'s of fuel pressure, hit the starter, starts great.

I fail to understand why it did not get a good ground where I 1st hooked it up, yet one thing is clear, for some reason it did not. Sometimes we forget how important the ground wire is and just because it is tightly bolted to a portion of the frame does not mean its grounded good. I'm just glad I thought about it and did not pull the tank back off.

Thanks for posting back how it went.

Good job on getting the ground working good.

Yes ground is as important as the neg. wiring.
Grounds can be tested with a volt meter.
With a voltage drop test.

You may have had some rust or paint where you bolted it up !!!!!

When ever I bolt a ground to frame I always scrape off or grind off rust and paint around the bolt area.

[Jerry80871852]

Electrical plug going to the TPS has 3 pins. Looks something like this.

^ ^
^

Voltage between the top 2 measures, 1.5

Voltage between the one on the left & bottom one, 4.98

I might add in case this would make any difference, made a trip to town and just got home, I had the TPS unplugged so that I would not have a high idle.

[MT-2500]

Originally Posted by Jerry80871852

Electrical plug going to the TPS has 3 pins. Looks something like this.

^ ^
^

Voltage between the top 2 measures, 1.5

Voltage between the one on the left & bottom one, 4.98

I might add in case this would make any difference, made a trip to town and just got home, I had the TPS unplugged so that I would not have a high idle.

You are a little high on sensor voltage to pcm
Black wire is ground.
One wire should be sensor reference voltage around 5 volts and should not change when you apply gas.

Now here is what you need to check!!!!!!
The wire or feed wire to pcm.
Specs are .32 volts to 1.28 at idle/close throttle.
With key on engine off open throttle slow and the sensor voltage to pcm should sweep even and steady from close throttle voltage .32 to 1.28 to 4.5 to 5 volts reference voltage with no drop outs or glitzes.
Even thow specs are up to 1.28 volts I would adjust it down to around .75 volts.

See if it does all of that.
And let us know.