1987 1/2 ton silverado no start 460k miles og

[Jheald65]

Hi -
 I looking for some information that maybe listed somewhere on the site but I haven’t  found it yet .. so I don’t mind if I’m referred out to an existing thread ...
  My son was driving the truck the other day when it started to stumble off the line from a stop light , under normal driving.. then it ran ok for a couple  hundred feet then died .
We had it towed home .
I’ll summarize the situation:
Truck will crank but not start
Have spark to the plugs per visual
Sprayed starting fluid into the throttle body - no change , engine doesn’t “try” to start at all .
Test of the 2 pin fuel pump plug at the drivers side tank is 6.5 v I’ve not tested the passenger side fuel pump yet to see if there is less than 12 v
Fuel pump relay plug , not the relay , was tested and have 12 v to terminal A , but when key is turned on , no 12v to terminal D , only 3.4 v
Full battery
No fuses blown
Fuel pump tested direct 12 v runs good
Pump removed and filter screen was brittle and broken .

I’ve not tested the ICM , passenger side fuel tank pump , or transfer valve ..any help or advice is totally appreciated

1987 1/2 ton Silverado
305 cu. in
TBI
700R4

[TonimusMaximus]

There may be an issue with the pumps wiring, but it should've done something when you sprayed it with starting fluid. That leads me to believe there's a spark problem. You can also check if the pump is working by undoing the fuel line into the motor and running it into a bottle. Turn the ignition on and see if she pumps.

[Irish_Alley]

something doesnt seam right these engines dont really require a whole lot to run. fuel, air/compression and heat. if you can spray fuel in the TB and you know you have spark then air/compression would be whats missing.
start here
http://forum.73-87chevytrucks.com/smforum/index.php?topic=24743.0

[bd]

460,000 original miles?  Does the engine share that mileage?  Has the timing chain ever been serviced?  Go ahead with the diagnostics presented in the linked guide, but add to that, "check the timing chain."  To check timing chain play read reply #4 in Re: 86 C10 Loping.

[VileZambonie]

Before you pull the seat out of the truck while standing on your head,

SES light come on with bulb check? Adequate spark from the ignition coil? Injector pulse?

Follow engine cranks but does not run diagnostic flow chart A3

CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN

Circuit Description :
This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in the tank. This chart should be used on engines using the Model 220 throttle body.

Test Description : Numbers below refer to circled numbers on the diagnostic chart.
A "Service Engine Soon" light "ON" is a basic test to determine if there is a 12 volt supply and ignition 12 volts to ECM. No ALDL may be due to an ECM problem and CHART A-2 will diagnose the ECM. If TPS is over 2.5 volts the engine may be in the clear flood mode which will cause starting problems. If coolant sensor is below -30~C, the ECM will provide fuel for this extremely cold temperature which will severely flood the engine.
Voltage at the spark plug is checked using Spark Tester tool ST 125 (J26792) or equivalent. No spark indicates a basic ignition problem.
While cranking engine there should be no fuel spray with injectors disconnected. Replace an injector if it sprays fuel or drips like a leaking water faucet.
Use an injector test light like BT8320, or equivalent, to test each injector circuit. A blinking light indicates the ECM is controlling the injectors.
This test will determine if there is fuel pressure at the injectors and that the injectors are operating.
Diagnostic Aids :
If no trouble is found in the fuel pump circuit or ignition system and the cause of a "Engine Cranks But Will Not Run" has not been found, check for:

Fouled spark plugs
EGR valve stuck open
Low fuel pressure. See CHART A-6.
Water or foreign material in the fuel system.
A grounded CKT 423 (EST) may cause a "No Start" or a "Start then Stall" condition.
Basic engine problem.

[roundhouse]

Could also try running a jumper wire from the battery to the fuel pump

[Jheald65]

Thanks for all the input , unfortunately I’m at work for another day so I won’t be able to test anything til then , thank you for the information .on diagnostics .. I’m going to start over at step one in case I’ve overlooked something and will update on my findings .. but yes to answer the question ,the truck is completely original, my uncle bought it in 87 new from the dealer . Drivetrain is all original, and has never broke down before .... aside from water pump s and alternators  this truck has never left me stranded....

[Jheald65]

So ,  have eliminated the fuel pump relay .
I do have :
12 v at the battery , 10.3while cranking
12 v at the fuel pump relay , with the priming lead for the pump coming on for 2-3 seconds then off .
12 v at the injectors 9.7 while cranking
Still 6.5 v at the fuel pump.

I worked backwards from the fuel pump to the tank selector valve and was not able to pull any power with my test light at Any of the pins on the plug ?
And no power up in the cab at the tank selecto switch on the dash either .. I’m getting ready to go over the schematic on the wiring now

[Irish_Alley]

have you tested the fuel tank switch yet or replaced it? not the valve but inside of the cab theyre known to get all gunked up and work sometimes and not others

[Irish_Alley]

also did you jump the red jumper wire on the relay and try to start it that way?

for the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6537.0

[Irish_Alley]

heres my little run in with the tbi. vile, capt and BD really helped out with diagrams and trouble shooting
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.0

[VileZambonie]

SES light come on with bulb check? Adequate spark from the ignition coil? Injector pulse?

[Jheald65]

so , I jumped the 12 constant from the electrical connection of the fuel pump relay plug (orange wire) to the tan /white. Wire of the plug . Now I have 12 v power at the tank selector switch in the cab , 12 v and power to the fuel pump on the drivers side ... and the fuel pump comes on nice and strong but like I said , it’s the constant power ... when jumped , the pump is always on . And that’s where I left off it got to dark ...bypassed the relay itself
 I did jump 12v wire from the pos terminal of the battery , to the 3 in pigtail of the fuel pump relay test wire ... nothing happens

[Jheald65]

Yes , SES light is on , there is spark at the plug , but unknown if injector pulse , as the pump is out if the tank , and the passenger side is empty due to a leak in the tank from year ago .

[Jheald65]

What does the fuel pressure module under the dash look like ? I see the diagram but can’t tell if what I see is the same thing ...