!995 Blazer Won't Start, Sometimes

[Firefox]

My daughter has a 1995 Blazer W/ 4.3 (W) engine.
She's had the fuel pump replaced twice, two pumps within 4 months of each other.
15 miles after the last fuel pump replacement and having sat for 24 hours, the Blazer wouldn't start again.
Two hours later it started.
Half an hour later it wouldn't start again.
The next morning it started right up.

I replaced the battery as it was kind of old anyway and it started afterward.
I'm not sure how the mechanic checked the fuel pump to be sure it was bad or if he even checked the electrical side of things first. Like making sure the pump was grounded and that there was power present at the pump.

Anyone else had this problem ?

thanks

[SUPERVISOR]

Fuel Pump Relay

[sparky672]

This happened to me just two days after replacing pump. Pump operation was intermittant.. sometimes only. Relay was fine.

I had to drop tank on a day when this was happening a lot. There is an emergency pump overide under the dash- jump 12 volts to this connector and the pump should run. This (if I remember properly) bypasses the relay entirely.

Anyhow.. with the tank lowered a few inches and power applied to the connector.. no pump noise at all. So I crawled under and tapped the top pf the tank. As I tapped, the pump went on and off.

I found a bad connection in the sending unit. Factory defect- the insulation was crimped in the connector causing this connection to work fine for years but a bit hot. I recrimped, cleaned connection, and fine ever since.

You might be better off with a new sending unit. There are 3 or more different electrical connections that could fail here.

Good luck.

[Firefox]

Is this the fuel level sending unit in the tank that you are talking about ?

It seems like if this were the problem the fuel level gage on the dash wouldnt work either.

thanks to both of you at any rate

[sparky672]

Yes- inside the tank you have the sending unit assembly, fuel pump, and pulsator.

The float, float arm, wiring harness, senser, and tubes are all part of the sending unit assembly which also has the brackets that hold the pump and pulsator.

The pump, pick-up screen, and pulsator are three separate parts.

[sparky672]

Originally Posted by Firefox

It seems like if this were the problem the fuel level gage on the dash wouldnt work either.

Not necessarily... it depends on the wire.

There are at least 3.
1. common
2. 12v power
3. signal back from level sending unit

If the wire to the pump power is flaky, then only the pump is affected.

There are several connections in the assembley. A main plug just underneath the round tank cover. A plug to the sending unit. And finally a plug to the pump. That's 3 plugs... a Y shaped pigtail with 3 connectors.

I'm not saying this is your problem, just pointing out that I had a bad connection to the pump and it was inside the tank. Something to consider.

[Firefox]

For those that might want to know......
I had the Blazer towed back into the shop and they pulled the fuel tank again, or at least got inside of it, after I told them what you all had said here.
What they found was the insulation on the hot wire to the fuel pump was discolored and stiff for about an inch from the connector due to it getting hot because of a loose or corroded connection. This was the harness inside the tank, the "Y" harnesss I think. They installed a new connector and removed the burnt section of wire.
The Blazer has been running fine ever since, about two weeks now. A record for it.
Didn't charge me foor towing it again and only charged $50 to fix it. I guess because it should have been noticed the first time they had it.
Actually it should have been noticed the first time the other shop had it.

Thanks to all for your help.

[sparky672]

I love it when things work out in the end.

[sparky672]

Originally Posted by Zach4u2c

Its the fuel pump relay, It happend to me...

??? The one who started this thread already posted the solution to his problem. Since his mechanic already changed the pump, I made an assumption that the control system outside of the tank was working properly and likely something was still wrong inside the tank. Your problem is a bit different, since during a failure you could easily see no power going to the fuel tank. -->>>

Originally Posted by Firefox

What they found was the insulation on the hot wire to the fuel pump was discolored and stiff for about an inch from the connector due to it getting hot because of a loose or corroded connection. This was the harness inside the tank, the "Y" harnesss I think.