What do I check next and how?

Tiny
RICK1950
  • MEMBER
  • 1990 CHEVROLET SUBURBAN
  • 290,000 MILES
My Suburban is a smallblock gasoline fuel-injected engine, automatic, two-wheel drive with high mileage. It has given reliable service for many years. Recently, at highway speed, the engine shut off after hitting a bump in the road. Would not restart. I checked ignition fire and it had plenty. Engine spun over fine but would not fire. Pulled fuel line loose at throttle body, no fuel. Pulled inline fuel filter loose, no fuel. Towed truck home, bought new fuel pump and relay and installed same. While checking fuel pump circuit, I found the ECMB fuse was blown, so I replaced it. Truck started right up and I drove it around near home for an hour with no problems.I turned off and started engine at least a dozen times. Next day I started truck and drove about a mile to the store. When I came out, the engine started and ran for maybe fifteen seconds and died. Engine spins, no start. Towed truck home and began checking everything again. Fuel pump is not running unless you hotwire to fuel pump relay test terminal. Relay wiring loom tests good(power with key on, fuel pump start circuit lights for two seconds when key first turned on). However, the new fuel pump relay seems to be inoperative. I got a new oil pressure switch and was about to install it, but I hesitate to do so until I figure out what's frying the relay. I rechecked fuses and they are fine, but should the ECMB fuse be hot all the time even when the key is off? I'm now wondering if I have a short or a loose ground somewhere. I've traced the wiring from the fuel pump to the fuse block, to the fuel pump relay, and under the dash to the ECM. Everything appears clean and tight including the ECM and its mount. However, the fact that the ECMB fuse was originally blown troubles me. I'm throwing a lot of money at this thing, but it's my only transportation. Any ideas? I'm tired, frustrated, and getting a little desperate. Please help me!
Do you
have the same problem?
Yes
No
Wednesday, October 12th, 2011 AT 1:33 AM

9 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Relax, we'll figure it out. If there is no power to the relay, I would start there. You checked all wiring from the pump, so it is good. Follow the wiring from the relay back to the switch to see if there is a problem there. I assume the fuse didn't blow this time. I have attached a wiring schematic of the fuel system to help. I don't know if you already have one.

Let me know what you find.
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 1:43 AM
Tiny
RICK1950
  • MEMBER
Jacobandnickolas, There is power to the relay and all wiring back to switch appears to be fine. Rick1950
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 2:10 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Sorry, I thought there was no power to the relay. Is there power out of the relay to the pump?
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 2:27 AM
Tiny
RICK1950
  • MEMBER
Jacobandnickolas, There is power through the harness when tested unplugged from the relay(power to ECM feed line, and ECM triggers 2 second start pulse) but no power when relay is plugged back in. That's why I assumed this new relay is now fried like the original. But, what can be causing it? Rick1950
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 2:39 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
The only thing I can think of is ground.
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 2:44 AM
Tiny
RICK1950
  • MEMBER
Jacobandnickolas, Pump relay harness tests fine, but no, there is no power out of the relay when plugged in. That's why I assumed this new relay is now fried. But what could be causing this? Rick1950
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 3:12 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Rick:

I am so sorry. I keep getting confused. I thought the power was making it back to the pump. If there is power in and not out, the relay has to be bad. What can cause it, too many amps being pulled from the pump, a short, bad ground.
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 3:16 AM
Tiny
RICK1950
  • MEMBER
Jacobandnickolas, Sorry, I can't retrieve your wiring schematic. Can you tell me how many ground points are indicated and where they are most likely located? I'm really not looking forward to taking the entire wiring harness loose under this dash chasing a "possible" ground issue. Maybe we could narrow the possible locations? Thanks, Rick1950
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 3:29 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
I'm not to send outside of the webpage, but if you give me your email, I'll resend it.
Was this
answer
helpful?
Yes
No
Wednesday, October 12th, 2011 AT 3:35 AM

Please login or register to post a reply.

Recommended Guides