Won't start. Thump fuel tank & it starts

[grienke]

Hi. I have a 1993 chev S10 pickup. On May 2, I when I tried to start it, it turned over but wouldn't start. I called a tow truck. The tow operator asked me to get in the cab. He told me to turn the key and while the engine was turning over he thumped the gas tank really hard. The truck started. He said he's seen lots of these situations and that the fuel pump is bad. I went to get it serviced. I explained what happened and the garage said that yes it's the pump. The pump, filter, and screen in the tank were replaced. On May 4, the exact same thing happened. This time I got it started by thumping the gas tank myself while a friend turned the key. The garage said they can't find out what's wrong. They tested the new fuel pump and it puts out the correct pressure. The engine has TBI. I asked the mechanic about a bad ground. He said he had cleaned the ground and it has a star washer. Any suggestions what might be wrong?

[MT-2500]

Originally Posted by grienke

Hi. I have a 1993 chev S10 pickup. On May 2, I when I tried to start it, it turned over but wouldn't start. I called a tow truck. The tow operator asked me to get in the cab. He told me to turn the key and while the engine was turning over he thumped the gas tank really hard. The truck started. He said he's seen lots of these situations and that the fuel pump is bad. I went to get it serviced. I explained what happened and the garage said that yes it's the pump. The pump, filter, and screen in the tank were replaced. On May 4, the exact same thing happened. This time I got it started by thumping the gas tank myself while a friend turned the key. The garage said they can't find out what's wrong. They tested the new fuel pump and it puts out the correct pressure. The engine has TBI. I asked the mechanic about a bad ground. He said he had cleaned the ground and it has a star washer. Any suggestions what might be wrong?

Welcome to your first post on AF.
If it starts after the gas tank thump points to bad fuel pump or wiring at fuel pump.
Ask the repair shop to show you how to jump the fuel pump prime connector and how to check for 12 volts on it.
Also ask them to run a amp ramp test on the fuel pump voltage if they have a lab scope or proper test equipment.
So the next time it does it you can check if you have 12 volt voltage to the fuel pump.
And go from there.
Ps do not forget to take the gas tank thumper with you. Good old block of wood or rubber hamer works good on them.
Good luck MT

[grienke]

I've had 5 more occassions where the truck wouldn't start. The mecahnic said to check for a spark.
1. I pulled the coil wire from the coil terminal.
2. I had someone turn the key to crank the engine
3. I held the coil wire maybe a quarter inch from the coil while the engine was cranking.
4. I saw a strong spark.
5. I then reconnected the coil wire and the truck started.
This worked on all 5 occassions. Any suggestions?

[MT-2500]

Originally Posted by grienke

I've had 5 more occassions where the truck wouldn't start. The mecahnic said to check for a spark.
1. I pulled the coil wire from the coil terminal.
2. I had someone turn the key to crank the engine
3. I held the coil wire maybe a quarter inch from the coil while the engine was cranking.
4. I saw a strong spark.
5. I then reconnected the coil wire and the truck started.
This worked on all 5 occassions. Any suggestions?

If you have spark the next step is to check for 12 power to fuel pump when no start.
You have to have spark and fuel pressure and injector pulse.
Find out what you are losing.
Ask the garage how to check for power on it.
Also a good check on fuel pump pressure may tell you somthing.
MT

[BLAZERBOY69]

My Guess Would Be Fuel Pressure.... When You Thump On The Tank, You Are Pushing It In Very Quickly, And It Increases The Pressure. Check Your Fuel Pressure Regulator For Good Pressure.