Wiring problems. Bad ground?

[sick620]

Not sure what year this truck is because it's hobbled together with a later model cab, and who knows what year l20b etc. It says it's A 73, but cab and wiring seems 76ish.. Anyways it has high output pathfinder alt, brand new starter, and it runs good when it starts.. If I put a fresh charged battery in it, or a battery that's successfully starting the other 620 no problems, it turns over OK and starts but it doesn't have a lot of umph as it turns the engine over. Seems to have a "draw" somewhere. After it turns truck over a bit and fires, if I turn truck back off and try to turn it over again it will really go slow, barely can even get it to turn over at all. If I try a third time or fourth, it won't even turn over at all. So basically a battery with 90% charge or better that's freshly topped off, or out of a running vehicle will get it to turn it over and start but it's weak, a battery with 70%-80% that would turn over any other vehicle at my house just fine, won't get it to turn at all. This is the second starter we've tried, new one helped a tiny bit, but not really, tried an extra known working ignition, didn't help. It was grounded from battery to firewall, grounded back to stock spot on engine, helped a little bit. I'll post some pics of under hood. But any ideas on what to check next?

[sick620]

[shacks510]

Starter needs to be grounded to the battery, or to a good chassis ground. I assume your truck has the battery in the factory location, so that makes it easy to run a ground directly to the starter. You can run a proper cable from the starter bolt or top bellhousing bolt to the battery negative. Make sure connections are clean from corrosion.

 

It'd also be a good idea to wire up a starter relay. The solenoid needs a good 12 volts. Old thin wiring, and a worn out ignition switch doesn't help.

[sick620]

Anyone know where this wire is supposed to go? It's running like this, is that wire important?

 

[sick620]

Don't mind bungie it was just holding battery down for temporary drive around Block.

 

[sick620]

[datzenmike]

That is not stock wiring so follow them to where they go and you'll have your answer.

 

 

 

Try re starting with booster cables connected to another vehicle. If still slow turning over with the starter then you know it isn't the battery.

 

What you can do that is cheap and easy is remove the battery cables and clean them and the battery posts. Make sure the cables tighten on securely or replace them. Next check the battery cable ends. The ground on the bolt on the head behind the fuel pump and the positive cable on the starter. Clean and tighten them both.

 

If still slow to crank, the starter may be bad. I've had a couple of starters that would start a cold engine but wouldn't re-start a warm one.

[sick620]

Oh I should also include, that if you put a battery in it that is a healthy fully charged one, it kills it in a day just sitting, so dead that the heater blower won't even come on or running lights.

[datzenmike]

Yes, it was converted over to internally regulated alternator but the auto choke relay is now permanently wired ON at all times. The choke isn't on with the key off, but the relay is. Mine would go dead in about two days. Unplug the choke relay on the fender and splice the Blue choke wire on the back of the carb to the Red idle cut solenoid beside it to fix.

[banzai510(hainz)]

pull the neg battery cable then put a test light between the cable and the battery post if terst light goes on then theres a Battery drain

[soundboi]

Seems like symptoms of bad grounds.

 

mines used to do the same thing, i reinstalled a ground on my shockhead, engine lower block, my alt has a grounding wire to the back of it with a 8mm bolt. My matchbox frame is grounded to my body as well.

 

Im using welding wire and copper lugs for my battery connection, one directly on the starter. The stock starter wire goes to a relay and then to the starter solenoid .

 

no problems since, iv been searching for my problems since i got my car.

 

  I also installed a internal regulated sr20 alternator 100amps with a single run of 0g car audio wire.

i charge 14.4 with a cold idle and 14v under full load.

[banzai510(hainz)]

the white ed strip wire is usually the output of the alternator output  round lug. I thinkits the same electrically but not stock.

[DanielC]

Trucks can have some grounding issues not seen in cars.  A truck has four main parts.  An engine, the cab, the bed, and the frame.  All these parts have to have a good ground back to the battery.

 

On a 521, the battery negative connects to the engine cylinder head.  From there, a pigtail goes down to the frame of the alternator.  There is a second wire from the alternator frame to one of the screws that hold the voltage regulator to the inner fender, grounding the cab.

 

If this ground goes away, the electrical things that are grounded to the cab sheet metal try to ground through the engine controls, on a 521, that is the throttle cable.

 

On my 521 trucks, I run a short jumper around one of the rubber engine mounts.  I have also found the tail lights work better if you ground the tail light frame directly to the frame of the truck, instead of the bed of the truck.