1988 bronco wont run!

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Bronco_addic

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I have a 1988 bronco with a 5.0 EFI. I just recently rebuild my engine and ever since I first fired it up i can not get it to run right. I did the cam break in on my first start up and put a vacuum gauge on it and did a compression and leak down test to be sure none of my cam lobes had flattened. my engine just will not run right, it takes 2-3 10 second cranks to get it to start. when it does start it runs like total garbage and shutters and misfires like crazy. I have tested everything and im at a total loss at this point. ill post all my results below. if you need anymore details i can provide them. i also found allot of gasoline in my oil.

FUEL

  • fuel pressure = 135-145
  • all 8 injectors brand new and clean
  • clean fuel rail
  • new fuel pressure regulator
  • new (inline) fuel pump
  • new (in tank) fuel pump
  • 12-13 volts to all injectors
  • all injector plugs are pulsing with a noid light 
  • new fuel filter
along with fuel the engine runs fine with acetylene in the air intake witch is odd considering all of the info above.

SPARK

  • new ignition coil
  • new plugs
  • new wires
  • new cap
  • new rotor 
  • ignition coil sparks 
COMPRESSION 

  • all 8 cylinders at 150-160 
  • leak down test, none are leaking
TIMING

  • Steady needle with a vacuum gauge so valves should be okay
  • timing set at 10 degrees BTDC
VACUUM

  • 12 inches at idle with steady needle 
  • smoked and no leaks
  • retraced vacuum diagram and all lines are there and in place
SENSORS 

  • map sensor = good
  • TPS = good 
  • IAC = good
  • O2 = good
  • ignition module, my ignition coil sparks so i assume that means that my module is good?
this is allot of info to take in so if you need and more info let me know. ive been fighting this thing for 7 months after my first start up and i honestly don't know where to begin.

 

miesk5

96 Bronco 5.0
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Yo Bronco_addic,

Welcome!

Is the fuel pressure in kPa or psi? Either is way TOO high.

Is the FPR a Motorcraft unit? If not it could be faulty. Or there is a return line kink or restriction because the engine runs fine with acetylene, hence no need for a return line.

...

The gas in oil is a rich condition;

02 sensor, you wrote good for it & the other sensors. Were these tested or new?

...

Since you found no vacuum leaks you can rule out a leak in FPR or its hose. But vacuum should be a little higher, 15 to 20. Low engine RPM could cause this; and you ruled out another possible cause such as low compression; an open throttle plate will cause lower a vacuum reading.

...

Misfire;

Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0 - engine miss, spark knock, buck/***** surge and other driveability concerns; MIESK5 NOTE; The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur. To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap.

See Diagrams @ http://www.supermotors.net/clubs/superford/vehicles/registry/media/299011

by Ford via tank92

...

coil sparks so module is OK & PIP (Profile Ignition Pickup) sensor inside distributor is OK.

...

Any codes?

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19

http://broncozone.com/topic/14269-code-reader/?pid=74587&mode=threaded

Some basics;

The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test.

If you can, run it or run it around to heat the engine up and shift thru all gears including Reverse.

Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual & release clutch.

Then turn off engine, all accessories/lights (close driver's door) , etc.

Do KOEO test First

Post Code(s) here according to:

KOEO

&

KOER, if possible

 
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Bronco_addic

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Sorry the fuel pressure was a typo, it's at 35-40 psi. The sensors were tested and all tested good. I'll double check my wire routing. I'm waiting on a new gas tank so I'm stuck till that gets here. One other thing I forgot to mention, the engine runs fine when you rev it up but say I revved it up to any rpm and held it at that rpm it would start to miss fire and dog down but has no trouble getting to that rpm. I'll get those codes once I get my new tank and can warm up the engine and post them here. Thanks!

 

miesk5

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Yo, ok.

Hope the engine can warm up to do koer!

BTW, you should see just 2 digit codes, such as;

DTC 41; "...KOEO; No HEGO sensor switching detected or disconnected. HEGO is bad, not connected, or missing. KOER; HEGO sensor indicates system lean. HEGO is going bad, missing."

DTC 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 & 565 are received , Check for proper HEGO Ground; in Catalytic Converter Diagnosis TSB 91-12-11 for 86-91 Bronco, F Series, & Econoline

Publication Date: JUNE 12, 1991

LIGHT TRUCK: 1986-91 BRONCO, ECONOLINE, F-150-350 SERIES

1988-91 F SUPER DUTY, F47

ISSUE: Lack of power or a no start condition may be diagnosed as an exhaust restriction caused by a plugged catalytic converter. A plugged catalytic converter (internal deterioration) is usually caused by abnormal engine operation.

ACTION: Diagnose the catalytic converter to confirm internal failure. Refer to the Catalyst and Exhaust System Diagnostic Section, in the Engine/Emissions Diagnostic Shop Manual and the following procedures for service details.

SERVICE PROCEDURE

1. Lack of proper HEGO operation may cause, or be the result of a rich or lean fuel condition, which could cause additional heat in the catalyst. Perform self test KOEO and KOER, service any codes.

NOTE: IF TWO DIGIT CODES 41, 42, 85 OR THREE DIGIT CODES 171, 172, 173, 179, 181, 182, 183 AND 565 ARE RECIEVED, CHECK FOR PROPER HEGO GROUND.

If the HEGO ground is good, the following areas may be at fault:

* Ignition Coil

* Distributor Cap

* Distributor Rotor

* Fouled Spark Plug

* Spark Plug Wires

* Air Filter

* Stuck Open Injector

* Fuel Contamination Engine OIL

* Manifold Leaks Intake/Exhaust

* Fuel Pressure

* Poor Power Ground

* Engine Not At Normal Operating Temperature

* HEGO Sensor

2. Spark timing that is ******** from specification may increase exhaust gas temperature and shorten catalyst life. Refer to the following procedure for service details.

a. Check spark timing. Check base timing with spout disconnected. Set base timing to the specification on the vehicle emission decal.

b. Check computed timing with spout connected.

NOTE: COMPUTED TIMING IS EQUAL TO BASE TIMING PLUS 20° BTDC ± 3°.

3. Misfiring spark plugs may cause an unburned fuel air mixture to pass through the catalyst, which could cause higher than normal catalyst temperatures. Refer to the following procedure for service details. Check secondary ignition, hook the vehicle up to an engine analyzer and check for a secondary ignition misfire.

NOTE: SERVICE ANY ITEM THAT IS NOT PERFORMING AT PROPER SPECIFICATIONS BEFORE CONTINUING.

4. Fuel pressure that is too high may cause rich air fuel mixtures to pass through the catalyst which could cause higher than normal catalyst temperatures. Refer to the following procedure for service details.

a. Check fuel pressure, install fuel pressure gauge, start and run the engine at idle. Fuel pressures between 28 and 34 PSI are typical (4.9L typically is 15 PSI higher).

b. Disconnect the vacuum line going to the fuel pressure regulator. Fuel pressure typically jumps to 40 PSI ± 3 PSI (4.9L typically is 15 PSI higher). Visually inspect vacuum line for raw fuel.

NOTE: FUEL PRESSURES ABOVE THESE VALUES SHOULD BE CORRECTED. HOWEVER, THIS MAY NOT BE THE CAUSE OF THE CONCERN. SERVICE AS NECESSARY.

5. Throttle plates in the throttle body not returning to the proper closed position may cause excessive catalyst temperatures during downhill grades. Refer to the following procedure for service details. Visually inspect the throttle body and linkage for:

* Binding or sticking throttle linkage.

* Tight speed control linkage or cable.

* Vacuum line interference.

* Electrical harness interference.

NOTE: AFTERMARKET GOVERNORS, THROTTLE LINKAGE AND CABLES ASSOCIATED WITH POWER TAKE-OFF UNITS, MAY ALSO INTERFERE WITH PROPER THROTTLE RETURN. SERVICE AS NECESSARY.

6. It is extremely important that all systems related to the engine and emission systems operate properly.

a. Visually inspect the engine compartment to make sure all vacuum hoses and spark plug wires are properly routed and securely connected.

b. Inspect all wiring harnesses and connectors for insulation damage, burned, overheated, loose or broken conditions.

c. Verify proper operation of the thermactor system. Thermactor systems that fail to dump thermactor air to the atmosphere properly or at the correct time can cause high catalyst temperatures.

d. Visually inspect thermactor system for damaged or kinked hoses and perform a function test on following components: air control valve, check valve, silencer, filter and the air bypass solenoid.

e. Verify proper operation of the engine cooling system thermostat.

Source: by Ford

...

DTC 42 O2 sensor voltage was stuck high for too long. (Rich).; "...Bad O2, or it's connector/wiring bad MAP sensor, Bad fuel pressure regulator, pull vac hose off, any gas in it or gas aroma means it's bad; Leaking injectors,restriction in fuel return line,or exhaust leak or clogged exhaust, lowering vacuum..."

 
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Bronco_addic

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Still waiting on a new gas tank but since I have the hanger assembly out was wondering if there is a way I can test my (in tank) pump while it's out? Can I submerge it in a bowl of gas and give the pump voltage so it flows out the top of the pump? Also my tank was really nasty and want to know if/how to clean my pump and hanger assembly.

 

Seabronc

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In that case, you might want to .consider using a compressed air line and blow out your fuel line.  Check the fuel intake screen to see if it is clean.  I'd be very careful running the pump via a battery direct connection, a spark could e a disaster.

:)>-

 

Daviddouglass79

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Good fuel pressure does not equal good fuel volume. I'd say you problem lies in the volume equation due to it running fine with the added accelerant.

 

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