T76s10

iTrader: (6)

1 more question, my fuel pump is hooked up to a toggle switch that's only a allowed to turn on when my accessories have power so when I turn the key to start my truck my fuel pump turns off. Do I need to wire the switch directly to battery + so it's running while it's cranking over? I have tried starting it both ways but neither seemed to make a difference but i'm thinking it needs to be running whole cranked over to maintain pressure

bczee

iTrader: (12)

There is usually two types of IGN Hots on the older GM Cars. Only One will stay hot while cracking and running.

The other will cut off as you go from Run To Start. That one may not be the one you want to use. This is can be verified as your radio and other accessories will cut out as you start the engine.

The other one that will stay hot in both Run and Start, usually will powers the Ign Coil. Trace it out in your harness or FSM diagram. Most liely should pick up power for your Manual Switch.

Question, why not just use the PCM to activate the pump ?

BC

Not sure that is your problem, But remember that the PCM, if used for activation of the Fuel Pump Relay will power it up for a second or two an then then cut out, if the PCM is sensing enough RPM, it will then re-activate the Replay for the pump.

bczee

iTrader: (12)

on your ground, yes a ground is a ground, but the path that the circuit takes for a ground may cuase high resistance. If some piece of electrical has to get is ground from going through many high resistance wires and route.. your going to burn something up or it will not function correctly due to the High Resistance that the circuit takes.

Just add the ground as I noted, it is only a little be of extra work but will ensure you have good ground as needed. And make sure you add that ground from the battery to the Block, frame and body.

Remember that some things are mounted with rubber or poly (Body mounts, etc) and will not conduct well.

BC

SS409

The ground from battery should be bolted to block with a clean bare metal surface. You should have a ground strap from block to body, and one from block to frame. The ecm should be grounded to the block with your engine harness.

The fuel pump should be ran off a relay with the ecm triggering the relay for priming and crank & run modes, do not run it straight off the battery!

Also check the temp sensor on drivers side head, make sure it is connected if the ecm does not see the correct engine temp, it will not start.

What year engine is this? What ecm are you running.

I can help you more, if I have more info.

Thanks

T76s10

iTrader: (6)

i am using a toggle switch for the fuel pump because a buddy of mine said at the track he goes to you need a switch to cut off fuel supply and thats the track ill be going to. i did the whole wiring from scratch and i tapped into the steering column and i only used a total of 4 wires. 2 for ignition and 2 for accessories. as long as the switch is hooked up to 12v all the time, as long as i flip it a few seconds before ignition, it should still start right? or will the ecm think that no fuel is going to the engine and not start? ill add in the ground that im missing from the engine to the frame and from the firewall to the engine. i will also relocate the injectors and ignition coils ground to the engine. i think that way everything will be grounded to chasis. my engine is a 2000 5.3 and the ecm is from a 1999 4.8.

T76s10

iTrader: (6)

the ECT sensor is indeed plugged in. heres a diagram of what i have in my truck. tell me if this looks right



my battery is in the bed of my truck and it doesnt make sense to run a wire from my battery negative to my frame and run another negative from my battery to my engine block so i will run the negative from my battery to my frame and from my frame to my engine block and from my engine block to the firewall.

bczee

iTrader: (12)

Many have made this same Assumption and have found that they were wrong. Highly suggest you run a 0 or 1 grounding wire from the battery to up front and/or the block.

Also.. If you running your Switch/relay to a battery (even if it is IGN powered), you really leave a lot on the table for safety. Should you get in a accident and forget to turn the switch off or you are unable to turn the switch off for what ever reason, ... Kaboom !, rosted car and driver... You better hope that someone will be around to turn the power off via the rear master cut off switch.

Just my option... and 2 cents..

BC

T76s10

iTrader: (6)

Yeah off it werent in the rules to have a switch for the fuel pump I wouldn't have done yet But everyone else I race with has one cause of track regulations so whatever. I'll pick up some 0 gauge wire and run it too the block but I dont have any other choice but damn is expensive

some dude

once upon a time this mechanic (me) was putting a clutch in a geo metro and forgot to hook the batt to engine ground back up and attempted to crank the car... i got to spend the next 4 hours putting a clutch cable in the car after it caught fire and siezed up.

you NEED to have a ground directly from the batt to the engine even if the battery is located inside your right rear tire...

seriously.

dumb question, why dont you just use the ecm to control the fuel pump and run a couple wires into the cab with a toggle switch to break the control circuit for the fuel pump relay?

some dude

also i would recomend using the + side of the FP relay control circuit just incase the wire grounded at some point so your fuel pump doesnt decide to stay on till it blows up

SS409

In this diagram, the starter is not grounded, because the block is not grounded.

You have to ground the battery to the block! Period!, it is the main ground for the S10's electrical system.

The block is isolated from the frame & body with mounts and bushings,
so the starter will not get a good ground with the battery ground bolted to the frame.

The starter will not get the current it needs to crank over the motor and will burn up the starter!

That is why the factory bolts the ground to the block. Grounds are just as important as the power wire, and are overlooked a lot.

If you need a switch for the fuel pump, just wire the ecm's fuel pump trigger to a switch then to relay, that way you can still kill the fuel pump any time you want, but the ecm still has control of the fuel pump.

Thanks

some dude

a revised version of what i said...

SS409

Yep, I didn't see your post till after I posted mine.

i guess great minds think alike

some dude

lol yea but i caught a geo metro on fire!

SS409

You say that like it's a bad thing! LOL

Just kidding, Fire! when working on car's is never good!

Well some times we learn things the hard way! LOL

some dude

yea, anytime you can stab a trans with one hand and start bolts with the other without breaking a sweat it deserves to burn.

T76s10

iTrader: (6)

Thanks for the input guys. Yeah in that drawing I meant it to have the block grounded. Only thing I was really confused about was why the block needed to be grounded to the negative on the battery and not to the frame when in the end the battery and the block are both mounted to the frame. But this it's the first time wiring EVERYTHING on a car other than doing stereo wiring and systems. So if out takes buying more wire then I'll do it. You guys know more than me for damn sure

SS409

it's good that you mentioned, stereo systems.

If you had a stereo system with amps, and did not ground the system good enough, what would happen?

When you turned up the system, the amps would heat up and go into protection.

Same thing is happening with your starter, by not having the block grounded good, the starter is not grounded good enough and getting hot causing slow engine cranking.

The starter takes a lot of current to crank over the engine, and it needs the best ground it can get.

The best ground is from the power source "The Battery".

So since the starter is grounded by the block, the block needs the best ground.

It is also just as important that the ground surface is clean bare metal.

Hope this helps you understand it better, Thanks

T76s10

iTrader: (6)

That makes sense now. No wonder why the starter is going so slow so it got cooked because my block isn't grounded. The only difference with wiring systems it's all the amps I have wired had a safety in them and wouldn't start unless it was grounded good enough. Wish I was smart enough to ground my block before I roasted my starter. Atleast now I know

the_merv

iTrader: (88)

The block is mounted with rubber motor mounts...zero transfer of ground.

I ground the Engine first no matter what..alot of essentials in that harness that need all the ground they can get.