96' Blazer - Starts and Dies after 30 Seconds

I've been searching so forgive me if this sounds familiar.

I was on my way home from the airport last night on the I-10 here in Phoenix. I was doing 70mph and suddenly, without warning, I lost the engine RPM. I mean the engine, with no sputter typical with running out of fuel, simply dies.

I get a tow home and start going over everything I know. I check obvious stuff like fuses, battery, and oh yeah there is fuel in the truck. I pulled the battery, put it on charge for an hour to give me a good battery to use. I run a lead from the positive terminal to the fuel pump test wire (looking from the driver side it is on the left). I listen and hear the fuel pump running. I get in...start the engine...it runs for 30 seconds then dies much the same way as on the freeway.

In the glove compartment there are three relays, one of which I believe is related to the fuel delivery system. I switched a couple around, and try to start...no go. I switch them back to the original way they were and nothing. I run the lead to the pump test wire again...this time...no buzz from the fuel pump. I gave up for a few hours, went back and it started again, ran for about 30 seconds and dies again.

I am at total loss:banghead: as what this could be and would like some pointers on where to start to eliminate systems from what could be causing this. What is sad is that this truck has been running well for years and I have been keeping it up with regular maintenance. I am going to be disappointed if I am missing something silly like a fuse I am not aware of.

Thakns for not flaming me and any help you may be able to give.

this happened to me ,did you check your distributor cap.mine did that and that's what it was.i was driving around 40mph and my truck just died.no signs or anything

I've been searching so forgive me if this sounds familiar.

I was on my way home from the airport last night on the I-10 here in Phoenix. I was doing 70mph and suddenly, without warning, I lost the engine RPM. I mean the engine, with no sputter typical with running out of fuel, simply dies.

I get a tow home and start going over everything I know. I check obvious stuff like fuses, battery, and oh yeah there is fuel in the truck. I pulled the battery, put it on charge for an hour to give me a good battery to use. I run a lead from the positive terminal to the fuel pump test wire (looking from the driver side it is on the left). I listen and hear the fuel pump running. I get in...start the engine...it runs for 30 seconds then dies much the same way as on the freeway.

In the glove compartment there are three relays, one of which I believe is related to the fuel delivery system. I switched a couple around, and try to start...no go. I switch them back to the original way they were and nothing. I run the lead to the pump test wire again...this time...no buzz from the fuel pump. I gave up for a few hours, went back and it started again, ran for about 30 seconds and dies again.

I am at total loss:banghead: as what this could be and would like some pointers on where to start to eliminate systems from what could be causing this. What is sad is that this truck has been running well for years and I have been keeping it up with regular maintenance. I am going to be disappointed if I am missing something silly like a fuse I am not aware of.

Thakns for not flaming me and any help you may be able to give.

When it quits check for lose of fuel pressure and or good hot blue spark to all spark plugs.
What is the fuel pressure reading when it quits?
Has any check engine lights be on?

The problem you are experiencing is typically a fuel pump or an ignition switch. Don't overlook the ignition switch- seems hard to believe that at 70 mph it would be the ignition switch, but if you do some research you will discover it is common.

Mine did the EXACT same thing that the original posters vehicle did, doing 70mph in fact. Got over to the side of the freeway safely and checked all that I could but could find nothing wrong.

Starts and runs for 30 seconds, then died. Over and over.

It turned out to be the cat-converter. Worth checking into if it is a high-mileage vehicle and the cat has never been replaced.

I have had a similar experience, on 2 vehicles. In one case it was the crankshaft position sensor. On the other the camshaft position sensor. However as MT2500 says "Remember proper testing gives us the answer to many problems."
Do some basic trouble shooting checking for spark and fuel or vacuum leaks.

I have had a similar experience, on 2 vehicles. In one case it was the crankshaft position sensor. On the other the camshaft position sensor. However as MT2500 says "Remember proper testing gives us the answer to many problems."
Do some basic trouble shooting checking for spark and fuel or vacuum leaks.

First check the fuel pressure 58psi- 60psi. If that is okay Check to see if you have spark. You might also have your map sensor tested several time until it gets warm to see if it malfuctions. If check engine light is on what are the codes that might help as well.

First check the fuel pressure 58psi- 60psi. If that is okay Check to see if you have spark. You might also have your map sensor tested several time until it gets warm to see if it malfuctions. If check engine light is on what are the codes that might help as well.

I have to disagree 58 to 60 is not enough to run these trucks 60 is minimum. Mine read 60 and still gave me problems at startup. I replaced my pump with a acdelco and it now reads 62 and haven't had a issue since. You need above 60 on cold starts.

Here's something not yet mentioned and a quick cheap fix if this is the problem ... sounds like it might be.

If fuel pressure is right near 60psi then a bad fuel filter will allow the engine to run for a period of time. As fuel is used the fuel pump struggles to push fuel through the filter to meet the 60 psi minimum requirement on the fuel rail. Once you drop below this the injectors will just not fire.

This can also lead to a situation where the car may misfire a few times and then will just not start. This just happened to me last weekend. I was driving about 60mph and then the car just lost all power and died. I got it started briefly and drove at slow speed for about 2 miles home and it died in the driveway. After that nothing.

I changed the fuel filter and it fired up immediately and is now perfect. Read the thread on fuel filters. Take the filter off, drain the fuel and blow into it and you will feel the resistance ... compare to a new one and you will be convinced this may be at least part of the solution.

One last point I forgot to mention ... if checking the pressure without the engine running but the ignition on ... a partially clogged filter will still register a high psi 60+.

Once the engine is started and the injectors are firing and using the pressure the fuel pump won't keep up and the pressure will likely drop ... causing the engine to stall.

Again... hope this helps.