98 Chevy 3500hd Fuel Gauge Not Working

[98Towtruck]

My 98 Chevy 3500HD,454,5spd,2wd truck has a problem with the gauge not working.I replaced the fuel pump with new DELPHI from GM dealer,replaced the cluster with another that worked in other truck.I figured somewhere between the cluster and pump is a problem,But it also has a hard starting problem,in the morning it starts fine,but after that it takes 10-30 seconds before starting.Sometimes I have to cycle key on/off to get it to start,the pump runs when I first turn key on,and if it doesnt start,it runs when I turn key off,but will not run when I turn key to ON.The truck has a relay and another box under cab on frame rail,it this the problem?Help its getting over my head.I have a GM tech that has the same problem on his 98 GMC 3500HD,and when he is stumped,I get scared!

[minibike132]

Single or dual tank? Did you replace just the pump or the whole module, could you provide the part number you replaced? It doesn't sound like your percieved fuel level and hard start complaints are the same thing, these are two completely different circuits unless they happen to share a connector that is bad. I would start chasing on the level problem first since it is all the time (it's all the time right, thats what it sounds like here). You might get lucky and fix them both at the same time but I wouldn't hold your breath. With the key on key off thing you were describing, if you are turning the key on, then cranking then off then on again right away and expect to hear the motor you will not. It's not supposed to run right away after a key off.

[L29er]

for hard starting, if it blows alittle bit of smoke after a hard HOT start consider injectors leaking or bad fuel reg (located drivers rear under intake) i`ve had problems with both, and this "relay and box" under cab sounds suspicious.... if you can try and inspect it for electrical corrosion...

[minibike132]

for hard starting, if it blows alittle bit of smoke after a hard HOT start consider injectors leaking or bad fuel reg (located drivers rear under intake) i`ve had problems with both, and this "relay and box" under cab sounds suspicious.... if you can try and inspect it for electrical corrosion...

 

It's just a guess but that relay and box thing is probably abs or a.i.r. related.

[L29er]

probly...

[98Towtruck]

I replaced the entire fuel pump module from GM dealer.The truck has started smoking a little white smoke in the last couple of weeks.This sounds like a good lead,When this cranks for 10-20 seconds and then fires up,it smells like raw fuel,I will check injectors and regulator.Now for the fuel level problem,I tested the connector where the connector plugs into the module,it changes as I move the float up and down simulating the level change,The sensor works in the tank.I replaced the cluster again with a working gauge,it does not work when in my truck.Is there a way I could run a new wire from the sensor to the cluster?I hate rigging things,but I am at wits end.Which color or position is the wire?Thanks

[minibike132]

You are leaving something out,

I tested the connector where the connector plugs into the module,it changes as I move the float up and down simulating the level change,The sensor works in the tank.

 

What changes? Does the reading on the cluster change? Do you have a voltmeter hooked up and that is changing? If so what setting is it on and where are the leads placed, also key on eng off or key off?

 

I wish it could be as simple as running a wire. The VCM is supplying a 5v ref to the sensor and then reading the difference. The VCM is then sending a signal to the cluster. I'd have to be a little smarter than I am or have more time on my hands then I do to figure out how to fool this thing. We may not want to fool it though. That 5v reference supplies alot of things so if there is a problem there it's best to figure out where the problem is at.

 

Before we get too involved here do you have a good multimeter?