Hello, my son is having a little trouble out of his 2003 Tahoe. It died on him the other day and we suspected fuel pump because we didn’t hear the pump coming on. We replaced the pump but still no power to pump. Today we hot wired the pump to get it to run but it would still not crank. All fuses and relays seem to be fine. It will try to crank once then when you shut it off again and turn the switch there’s nothing. Any help would be appreciated.
A little help with my son’s 2003 Tahoe
- Thread starter Ash4l
- Start date
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Welcome to the forum from Colorado!
Verify that the battery is fully charged and has cranking capacity. How old is it, and has it been tested lately?
Did the pump run when you hot wired it? Use a fuel pressure gauge while you hot wire the pump to see if it runs and brings the pressure up.
I suggest bypassing the starter relay to see if the main cables are intact and can handle the current. This thread shows how to do that, but there will be several YouTube videos, so do some searching if you'd rather:
www.tahoeyukonforum.com
I'd also suggest doing a voltage drop test:
Verify that the battery is fully charged and has cranking capacity. How old is it, and has it been tested lately?
Did the pump run when you hot wired it? Use a fuel pressure gauge while you hot wire the pump to see if it runs and brings the pressure up.
I suggest bypassing the starter relay to see if the main cables are intact and can handle the current. This thread shows how to do that, but there will be several YouTube videos, so do some searching if you'd rather:
no crank no start intermittent problem
Sorry to bring this thread back from the dead. My truck does the same thing but it will start with my remote start with no problems. I replace the starter last winter. Should I be looking at the ignition switch? Thanks That would be a good place to look. I don't know what year make/model your...
www.tahoeyukonforum.com
I'd also suggest doing a voltage drop test:
rockola1971
Full Access Member
After checking Ign A and Crank Fuse and both negative and positive cable battery connections at the battery, starter and engine block ground(corrosion is usually the culprit here), I would suspect the ignition switch. If you are familar with how to use a voltmeter I can tell you where to check using the following schematics. I own (2) 2003 Tahoe LT's.
Attachments
Have @rockola1971 get you some test info before condemning the switch. In my experience there's nothing worse than introducing new parts as variables.
rockola1971
Full Access Member
Ckeck for 12v at dark green/white wire terminal of fuel pump relay socket. This will be the coil terminals of the relay. One will be ground and the other 12v when ignition is turned to crank. You will have to check this with relay pulled out. Other 2 terminals will be 12v hot at all times and the other is the feed for 12v to your fuel pump. While you have fuel pump relay pulled measure resistance of coil of relay. Diagram on side of relay will tell which 2 terminals lead to the coil.
I don’t think it’s the wiring of the fuel pump that’s bad. We changed out the ignition switch thinking it may be it. I was wrong about changing it earlier. It was the ignition lock. I couldn’t remember, anyways that wasn’t the cause. We bypassed the relay and and had full voltage on the lines. Something somewhere is causing it not to get the power all the way around to run. It’s very strange. Never had anything like this before.
rockola1971
Full Access Member
I went back through your post and it appears you have no crank or intermittent cranking issue. When it comes to relays there are actually 2 circuit going to a relay. Usually a high amp circuit for feeding power to (in this case) a fuel pump and then a low amp (control circuit) to the coil. They are separate from each other. The fuel pump is fed directly from its own fuse. The coil to the Fuel Pump Relay is fed from the PCM after certain conditions are met. The PASSLOCK security system does NOT disable engine crank like most aftermarket alarm systems operate. It strictly disables the fuel pump after 5-10 seconds if the PASSLOCK is not happy or defective.
Quick and dirty check here is check for 12v on small wire (S terminal) of starter solenoid while someone is trying to crank engine. This will tell us whether we have a starter issue or a control issue. Do this check with a fullly charged battery.
