Not getting fuel - Help please

[kwilson512]

I just bought a 87 silverado (305 tbi), long story short I was driving it today and it quit on me. I'm not mechanically inclined at all so I am asking for a lil help trouble shooting my problem but I've narrowed it down to a fuel (or lack there of) problem.

I dont have a drivers side inner fender and it was wet outside, the electronic componets on the drivers side were wet and wondering if this could be the issue, before today the truck has run fine but I have never had it out when the roads were wet.

The fuel pump is pumping fuel to the tbi, i loosened up the line and its sending the fuel, I got spark but its not firing. I can get it running with starting fluid but it dies ...any ideas?

[glock35ipsc]

The pump could have failed, or is about to fail. If you can get the fuel pressure checked, see what it is. TBI's need around 13-15 psi IRRC. Also, It could be the pressure regulator on the TBI, the fuel filter is plugged, or the return is plugged.

That's just a few things that came to mind right away..... I'm sure others will chime in.

[thehitchmaster]

are the injectors spraying?

[kwilson512]

Dont know if this will help any but the oil pressure guage was going haywire before it quit.

The injectors werent spraying.

[WestButteTruck]

Originally Posted by kwilson512

Dont know if this will help any but the oil pressure guage was going haywire before it quit.

The injectors werent spraying.

If your oil pressure guage was "going haywire", it's possible the moisture, or maybe something bigger, like no oil pressure caused the relay to shut down fuel. Since you are able to get it to run on starting fluid it's obvious is fuel related. But what is causing it could be a number of things. What's your oil pressure say? Do you have a garage you can push it into to let things dry out?

[rfmaster]

Originally Posted by WestButteTruck

or maybe something bigger, like no oil pressure caused the relay to shut down fuel.

This will only happen if main FP relay, which is controlled by ECM, is off. The oil pressure switch contacts are normally open (NO) when there is no oil pressure. GM put two set of contacts to keep FP operating just in case if FP relay fails for some reason. If you have oil pressure it should keep oil pressure switch contacts closed and FP will continue to operate. ECM has no oil pressure input so it will keep FP relay contacts closed even if there is no oil pressure in the engine - this is normal during initial cranking as it takes time for oil pump to build up oil pressure in the lubrication system. FP relay functionality is verified during POST sequence - it is important to make sure that elements in fuel control system operate before troubleshooting.

//RF

[raveer2000]

The injectors get signal from the Distributor module

[kwilson512]

Thanks for the help, I still welcome any/all ideas and will begin working on it in the a.m.. Gonna try and start with the inexpensive stuff and work my way up since its a $1000 plow truck.

[rfmaster]

Originally Posted by kwilson512

Thanks for the help, I still welcome any/all ideas and will begin working on it in the a.m.. Gonna try and start with the inexpensive stuff and work my way up since its a $1000 plow truck.

TBI system is relatively robust and can withstand harsh operating conditions, however water and electronics do not mix very well.

You'll have to perform series of checks

1) turn ignition key from on into run position, but do not attempt to start engine. The SES light in your instrument cluster should be on, blink off and turn on back to solid. At the same time fuel pump should come on for about 2-3 seconds and shut of. This is called POST during which ECM checks all sensors and controls. POST = power on system test. If there is no SES light verify that all fuses are good - blown injector or ECM power fuse will prevent engine start!

2) If you do not hear fuel pump come on during POST then either fuel pump relay (simple) or ECM ( not so good) are at fault. Fuel pump (FP) relay is mounted on the firewall - it is easy (and cheap) to replace.




All too often relay is OK but the socket has bad contacts.



The oil pressure sensing unit serves double duty - a) provides pressure indication to instrument cluster and b) provides fail safe contacts in case of FP relay failure. If FP relay failed and if you crank engine long enough the oil pressure sensor will provide DC power to fuel pump (once oil pressure builds up to about 4-6psi).



3) Ignition check - spark plug tester and see if there is spark during cranking. There are must be spark otherwise check ignition parts - distributor, coil, wires.

4) If 1-3 check out then it possible that ECM is not receiving distributor reference pulse signal (DRP) This signal tells ECM when to fire injectors. Check small 4-wire connector that plugs into distributor. Loose or moisture contaminated plug may be the cause. Verify 1-3 first and let us know.

//RF

[Jim85IROC]

Originally Posted by rfmaster

Stuff...

//RF

Thanks! That's a great post. Because I had a baby back in June, when my truck wouldn't run I had it towed to a trusted mechanic instead of doing it myself, and it's still there because he can't find the damned problem. As soon as it warms up I plan to go down there and work on it myself (should have done that in the first place!) and this will help me troubleshoot!

[kwilson512]

[kwilson512]

Installed a new filter, pump/sending unit and fuel pump relay and still getting nothing....nothings changed.

[kwilson512]

Anyone got a fuse box diagram for an 87?

[thrtsxchambers]

Her is what I have for the fuse box. It should cover 80-87 c10. Hope it helps.


A - Choke
B - Fuse - Heater / Air Cond.
C - Receptacle - Accessory
D - Receptacle - Ignition ( key on power)
E - Fuse - Auxillary Heater / AC
F - Fuse - Instrument Cluster Feed (gauges)
H - Fuse - Tail Lights, Courtesy Lamps
I - Fuse - Wipers
J - Fuse - Horn
K - Receptacle - Power Accessories & other Accessories
L - Receptacle - Battery (constant power)
N - Not Used P - Fuse - Turn Signals, Reversing Lamps
R - Fuse - Fuse - Radio & TCS (Idle)
X - Receptacle - LOS
Z -Fuse - Stop (brake) Lights, Traffic Hazard Flashers

[kwilson512]

Okay...the first sign of progress...I guess

I keep throwing the ECM B fuse (10amp)...any ideas?

[Desert1957]

I just went through this last summer on my neighbor's truck, It's an 87 like yours but with a 7.4 (454) engine. Ignition module went bad causing no reference to the ECM , so NO fuel pump. Installed a new ignition module (inside the distributor) and Fuel pump started working.

I know what your thinking, Module for no fuel pressure? , but this is how your system works.

Desert

[kwilson512]

I appreciate the help everyone...been looking around the world wide web and still feel like there are 30 different possible causes.

A little more info about my money pit of a truck..
-I have dual tanks, the drivers side tank is not functional. the passenger side one is.
-My fuel gauge always reads full - never leaves full
-About a week ago my nephew messed with the tank selector switch...I put it back and the truck didnt want to start for a good 2-3 hours...dont know why but it was hell trying to start it.....could it be as simple as the tank selector switch?

Thanks in advance

[kwilson512]

Okay switched out the tank selector switch ....same issues

It started again but seemed not to be running on all cylinders when started and blew the ecm-b fuse a couple more times...and back to square one only now I know the tank selector switch isnt the problem.

Also ...check engine light is working...I dont know enough but doesnt that mean my ecm is functional?

Brake light on too

[Jim85IROC]

Originally Posted by kwilson512

It started again but seemed not to be running on all cylinders when started and blew the ecm-b fuse a couple more times...and back to square one only now I know the tank selector switch isnt the problem.

My truck does the same thing when it does actually start and run... it acts like it's not on all cylinders. I've never checked the ecm fuse, though I have no reason to think that's blown.

[kwilson512]

OKay...it seems to be running fine now...trouble is I didnt do anything new..I have the air filter off right now so I guess the only variable between now and two hours ago is that. Maybe the filter/housing is touching a bare wire or the wire is worn but just eyeballing it the wires seem okay. Could it be my original thought that water caused this in the first place and it took a couple days to dry out?...if so I need to get the inner fender in there asap bc there is alot of corrosion on the panel.

[Jim85IROC]

Originally Posted by kwilson512

OKay...it seems to be running fine now...trouble is I didnt do anything new..I have the air filter off right now so I guess the only variable between now and two hours ago is that. Maybe the filter/housing is touching a bare wire or the wire is worn but just eyeballing it the wires seem okay. Could it be my original thought that water caused this in the first place and it took a couple days to dry out?...if so I need to get the inner fender in there asap bc there is alot of corrosion on the panel.

My problem had been intermittent for quite a long time too. First it ran fine most of the time, but would suddenly stall and not-restart. Then it got to where it wouldn't start most of the time. Now it almost never starts, but every so often, it'll start and run on a few cylinders.

So far, changing the plugs, wires, cap & rotor has been ineffective. Air cleaner assembly on or off doesn't make a difference.

[thrtsxchambers]

I have no inner fenders in mine and have been caught in the rain before but never had a problem. The only time I had a similar problem to your was when my fuel pump was going out, changed it , no problem. But if you have a loose or frayed wire it could cause a problem.

[Jonboy]

You may want to change the oil pressure sending unit as well. In 87, it also has the oil pressure switch built in. It will be above the oil filter on the left side. If the switch has gone bad it will not trigger the fuel pump relay. You may have a short in the wire there also.

[383tbi]

Originally Posted by Jonboy

You may want to change the oil pressure sending unit as well. In 87, it also has the oil pressure switch built in. It will be above the oil filter on the left side. If the switch has gone bad it will not trigger the fuel pump relay. You may have a short in the wire there also.

The sending unit on top of oil filter on the 87 is strictly for the gage.The switch that ties into the fuel pump relay is the one on top engine block next to distributor.

[kwilson512]

Thanks to everyone that help me work through this issue, still dont know exactly what the problem was but I know where to check to troubleshoot it when it happens again. If nothing else you guys made me fix or replace alot of stuff that had been ignored by the PO.

I plowed all day today, had no problems at all out of it....Another day or two like this any my $1000 plow truck is gonna pay for itself....Thanks again.