injectors?

luvlrd · 09-20-2007, 08:40 AM

i put a new gas tank in a 96 chevy 1/2 ton pickup was running to find out had a leak on the sending unit (but was running) replaced the sending unit and its getting gas to the motor but wont run and it it not returning please help thanks

**qldit** · 09-21-2007, 07:02 AM

Good Evening luvlrd, I am not familiar with that vehicle but as a general rule of thumb the system works like this.......

The tank fuel pump is operated by a relay, (usually located under the bonnet in the engine bay) the fuel is pumped to the fuel rail on which the injectors are mounted and fed from, the fuel pressure in that rail is maintained at a steady pressure by a relief valve at one end and excess fuel is returned to the tank. The flow of fuel through this rail is sufficient to ensure that fuel is usually being returned to the tank and inso doing provides an element of cooling for the injectors.

Your description suggests that fuel is constantly present, so in that your machine does not run, suggests that you may have either a computer or ignition problem.

If there is any chance you may have used jumper leads from another battery and had a slight mishap with connections it could be quite an expensive problem.

In that the pump would appear to be running (which is normally activated by the same computer power supply circuit) it sounds odd.

Have you checked all the fuses associated with the system ? (usually located in the underdash panel area)

Have you done anything apart from replace the tank and pump, I am not familiar with the term "sending unit".

Is that tank and the new pump suitable for an EFI system?

Others will have different ideas.

Cheers, qldit

oceanrunner · 09-22-2007, 07:11 AM

Good morning,

A few thoughts...

I'm not an expert but I own the same vehicle, only a 97. I replaced the sending unit and fuel pump as a unit which is all located in the fuel tank, as you know, and then I had a problem with the vehicle not starting. The fuel relay was good and there was a spark. Check those things first. Fuel pressure was good at the intake manifold. You can check that easily with a pressure guage at the pressure check valve on the fuel line entering the upper plenum (big plastic intake manifold looking thing on top of the engine). If the fuel pressure is good but slowly decreases after a few seconds, it is possible that the fuel pressure regulator is bad which is located under the upper plenum. It is also possible that the return line is clogged. Check that by blowing air through the return line. Check to see if any lines were pinched when you reinstalled the tank.

MY problem was a leaky fuel pressure guage which was evident from a puddle of fuel or clean spot under the plenum, near the rear right cylinder bank. I also found that the original "poppit" valves were so dirty that I installed a fuel injection "spider" micro injector unit which increased performance and fuel mileage greatly (300-400 dollars) and the vehicle runs better than it ever has.

Hope this helps.

09-20-2007, 08:40 AM	#1 (permalink)
luvlrd Registered User Join Date: Sep 2007 Posts: 1 OS: XP	injectors? i put a new gas tank in a 96 chevy 1/2 ton pickup was running to find out had a leak on the sending unit (but was running) replaced the sending unit and its getting gas to the motor but wont run and it it not returning please help thanks

09-21-2007, 07:02 AM	#2 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: injectors? Good Evening luvlrd, I am not familiar with that vehicle but as a general rule of thumb the system works like this....... The tank fuel pump is operated by a relay, (usually located under the bonnet in the engine bay) the fuel is pumped to the fuel rail on which the injectors are mounted and fed from, the fuel pressure in that rail is maintained at a steady pressure by a relief valve at one end and excess fuel is returned to the tank. The flow of fuel through this rail is sufficient to ensure that fuel is usually being returned to the tank and inso doing provides an element of cooling for the injectors. Your description suggests that fuel is constantly present, so in that your machine does not run, suggests that you may have either a computer or ignition problem. If there is any chance you may have used jumper leads from another battery and had a slight mishap with connections it could be quite an expensive problem. In that the pump would appear to be running (which is normally activated by the same computer power supply circuit) it sounds odd. Have you checked all the fuses associated with the system ? (usually located in the underdash panel area) Have you done anything apart from replace the tank and pump, I am not familiar with the term "sending unit". Is that tank and the new pump suitable for an EFI system? Others will have different ideas. Cheers, qldit

09-22-2007, 07:11 AM	#3 (permalink)
oceanrunner Registered User Join Date: Sep 2007 Posts: 10 OS: XP	Re: injectors? Good morning, A few thoughts... I'm not an expert but I own the same vehicle, only a 97. I replaced the sending unit and fuel pump as a unit which is all located in the fuel tank, as you know, and then I had a problem with the vehicle not starting. The fuel relay was good and there was a spark. Check those things first. Fuel pressure was good at the intake manifold. You can check that easily with a pressure guage at the pressure check valve on the fuel line entering the upper plenum (big plastic intake manifold looking thing on top of the engine). If the fuel pressure is good but slowly decreases after a few seconds, it is possible that the fuel pressure regulator is bad which is located under the upper plenum. It is also possible that the return line is clogged. Check that by blowing air through the return line. Check to see if any lines were pinched when you reinstalled the tank. MY problem was a leaky fuel pressure guage which was evident from a puddle of fuel or clean spot under the plenum, near the rear right cylinder bank. I also found that the original "poppit" valves were so dirty that I installed a fuel injection "spider" micro injector unit which increased performance and fuel mileage greatly (300-400 dollars) and the vehicle runs better than it ever has. Hope this helps.