99 suburban wont start

[gp428]

i am working on a99 2500 4x4. 7.4 Replaced 230,000 engine with 90,000 engine.I had to fix a bad oil leak from the oil pressure sensor .Replaced it and delivered it. Ran great Gal was driving at 50mph
Engine died and wouldnt start.she fried starter trying. Replaced starter,has no codes.59-60 lbs fuel pressure with key on then holds 50 lbs. 60 lbs while cranking. Has spark at plug.NO security light staying lit or flashing. flashes then goes out. Smell of unburnt fuel is strong. Also no oil pressure at gauge when cranking and her key fob doesnt work.

Please help if you can. Thanks.
E

[j cAT]

Originally Posted by gp428

i am working on a99 2500 4x4. 7.4 Replaced 230,000 engine with 90,000 engine.I had to fix a bad oil leak from the oil pressure sensor .Replaced it and delivered it. Ran great Gal was driving at 50mph
Engine died and wouldnt start.she fried starter trying. Replaced starter,has no codes.59-60 lbs fuel pressure with key on then holds 50 lbs. 60 lbs while cranking. Has spark at plug.NO security light staying lit or flashing. flashes then goes out. Smell of unburnt fuel is strong. Also no oil pressure at gauge when cranking and her key fob doesnt work.

Please help if you can. Thanks.
E

replacing the engine wires get damaged and grounds get not secured.

check for injector signals / fuses/ spark/ timing etc.

does it run with fuel placed into the throttle body ? if so recheck the fuel pressure/spec's. the 5.7 L engine requires 62-65psi key on engine off.

since it has strong fuel odor most likely a bad electrical issue with the ignition system.

when cranking engine see if the distributor rotor rotates.

[gp428]

The rig was driving for 2 weeks after the engine swap and before the oil leak.Engine is 454.What is the oil pressure supose to be with key on engine off? Today while cranking it over bad electical smell . Thought I toasted starter but it still turns over.Has slight kick back. Thanks/

[j cAT]

Originally Posted by gp428

The rig was driving for 2 weeks after the engine swap and before the oil leak.Engine is 454.What is the oil pressure supose to be with key on engine off? Today while cranking it over bad electical smell . Thought I toasted starter but it still turns over.Has slight kick back. Thanks/

I'm not sure on the 454 cu fuel pressure spec.

5.7L key on eng off is 62-65psi ..

when cranking you crank for 5 sec. off for 2 min. too much cranking you will cook the starter with not enough cool down.

heat on the motor armature will cause the motor to loose torque.

[777stickman]

'98 7.4 key on eng off fuel press=55-62, or so the shop manual says.

[gp428]

Originally Posted by 777stickman

'98 7.4 key on eng off fuel press=55-62, or so the shop manual says.

mine flashes to 59-60lbs and right away holds at 50lbs. Should it start with that pressure?If not would it be regulator or pump?Tomorrow will try starter fluid and check cap and rotor. Thanks.

[j cAT]

Originally Posted by gp428

mine flashes to 59-60lbs and right away holds at 50lbs. Should it start with that pressure?If not would it be regulator or pump?Tomorrow will try starter fluid and check cap and rotor. Thanks.

key on engine off the pressure should not drop fast down to the 50PSI. place the pressure gage on the fuel filter. see if this repeats if so then the fuel pump is defective.

if the pressure holds then the regulator or the injectors are causing the pressure drop.

[gp428]

Originally Posted by j cAT

key on engine off the pressure should not drop fast down to the 50PSI. place the pressure gage on the fuel filter. see if this repeats if so then the fuel pump is defective.

if the pressure holds then the regulator or the injectors are causing the pressure drop.

put the gauge on the fuel filter and got 0 pressure. Fuel was pumping. I thought gauge was broke so I put it on the fuel rail. 0 pressure with key on. I put air through the gauge and got pressure.Now fuel pump comes on intermitant with key on.Doesnt seem to be on while cranking.Still wont start with gas in tb.

[j cAT]

Originally Posted by gp428

put the gauge on the fuel filter and got 0 pressure. Fuel was pumping. I thought gauge was broke so I put it on the fuel rail. 0 pressure with key on. I put air through the gauge and got pressure.Now fuel pump comes on intermitant with key on.Doesnt seem to be on while cranking.Still wont start with gas in tb.

you may have a few problems. first you must have fuel pressure. that is step one.

so key on no fuel pressure at the fuel filter and you hear the pump running for the 2 sec time with first turning on the ignition from OFF to ON .

what this may mean with a new good pump is , the pickup tube is not properly installed or is defective. could also be you have no fuel in the tank !

the pick up tube if is has a leak , will not be able to suck fuel from the lower fuel level in the tank.

[gp428]

Originally Posted by j cAT

you may have a few problems. first you must have fuel pressure. that is step one.

so key on no fuel pressure at the fuel filter and you hear the pump running for the 2 sec time with first turning on the ignition from OFF to ON .

what this may mean with a new good pump is , the pickup tube is not properly installed or is defective. could also be you have no fuel in the tank !

the pick up tube if is has a leak , will not be able to suck fuel from the lower fuel level in the tank.

Thanks for the help. I put gauge on the fuel filter again and got 70- 80 lbs. 50 at the rail key on. No spark. Replaced the crankshaft position sensor still no spark. code po336. reinstalled cps nocode no spark.Today i replaced fuel pressure regulator,cap and rotor. It now builds 30-40lbs and falls right away. Wont hold pressure.Fuel pump runs for 2 seconds intermittently.Doesnt while cranking.Fuel pump relay?Runners look dry.Fuel pump pressure ok at 70-80 lbs?

[j cAT]

Originally Posted by gp428

Thanks for the help. I put gauge on the fuel filter again and got 70- 80 lbs. 50 at the rail key on. No spark. Replaced the crankshaft position sensor still no spark. code po336. reinstalled cps nocode no spark.Today i replaced fuel pressure regulator,cap and rotor. It now builds 30-40lbs and falls right away. Wont hold pressure.Fuel pump runs for 2 seconds intermittently.Doesnt while cranking.Fuel pump relay?Runners look dry.Fuel pump pressure ok at 70-80 lbs?

the pressure at the fuel filter was 70-80 psi and most importantly held pressure correct ? if it droped the fuel pump is bad.

if the pressure at the fuel filter held pressure then at the fuel rail drops quickly you have in injector / fuel reg / leak in the fuel delivery.

you have no spark . did you check the distributor for damage wear of the bearings/gear etc.

when cranking does the rotor rotate ?

with a manual check out the coil resistance and wiring.

this is a 5.7L engine the fuel pressure need be 62-65 psi key on engine off.

454 cu what did you find is the fuel pressure spec ? stickman says 55-62psi below 53 psi I would expect a no start.

[gp428]

Originally Posted by j cAT

the pressure at the fuel filter was 70-80 psi and most importantly held pressure correct ? if it droped the fuel pump is bad.

if the pressure at the fuel filter held pressure then at the fuel rail drops quickly you have in injector / fuel reg / leak in the fuel delivery.

you have no spark . did you check the distributor for damage wear of the bearings/gear etc.

when cranking does the rotor rotate ?

with a manual check out the coil resistance and wiring.

this is a 5.7L engine the fuel pressure need be 62-65 psi key on engine off.

454 cu what did you find is the fuel pressure spec ? stickman says 55-62psi below 53 psi I would expect a no start.

I am stumped.Fuel pump holds 80 lbs.I Took the fuel rail ,injector and fpr assembly from the old engine and put it on. Fuel rail pressure is 56 and then holds 50lbs. Reinstalled the new fpr on original fuel rail and reinstalled. 56 and then holds 50 lbs. That makes three.The original,the new and the old motors.
distributor seems to be good. New rotor does turn while cranking.

Replaced oil pressure switch. Should there be oil pressure at the gauge in instrument panel when key on or while cranking? I have none.
Thanks

[j cAT]

Originally Posted by gp428

I am stumped.Fuel pump holds 80 lbs.I Took the fuel rail ,injector and fpr assembly from the old engine and put it on. Fuel rail pressure is 56 and then holds 50lbs. Reinstalled the new fpr on original fuel rail and reinstalled. 56 and then holds 50 lbs. That makes three.The original,the new and the old motors.
distributor seems to be good. New rotor does turn while cranking.

Replaced oil pressure switch. Should there be oil pressure at the gauge in instrument panel when key on or while cranking? I have none.
Thanks

are you sure the regulator is correct for you vehicle ?

the oil pressure will not prevent a cranking start . this is bypassed.

is the security system on . that would prevent spark. any aftermarket anti thieft on this vehicle now or in the past ?

only after the engine gets running would the oil pressure switch cut out the fuel pump.

the fuel pressure is low , see if the gauge is out of cal use another.

check the ignition switch. check the ignition fuses for voltage with the key on engine off. also distributor/coil voltage. make sure your grounds/wires/connectors all correct and secure.

this problem does have too many issues for me to understand how it got this screwed up.

[gp428]

Originally Posted by j cAT

are you sure the regulator is correct for you vehicle ?

the oil pressure will not prevent a cranking start . this is bypassed.

is the security system on . that would prevent spark. any aftermarket anti thieft on this vehicle now or in the past ?

only after the engine gets running would the oil pressure switch cut out the fuel pump.

the fuel pressure is low , see if the gauge is out of cal use another.

check the ignition switch. check the ignition fuses for voltage with the key on engine off. also distributor/coil voltage. make sure your grounds/wires/connectors all correct and secure.

this problem does have too many issues for me to understand how it got this screwed up.

Thanks. No security light on. Fuel injectors are working. Verified before putting plenum back on. I have no spark at plug or coil.No codes.

Thanks for your help.