Engine Hard Starting

Ptstew

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Sep 21, 2017
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I installed a 1993 Cobra intake manifold with a 70mm plenum opening onto my stock normal starting and running 1991 Mustang engine. I also installed a 70mm BBK throttle body and new 19# injectors. I kept the stock ECM, idle control valve, EGR valve and 55mm 19# MAF. The engine is very hard to start especially when warm. The throttle must be varied and it finally fires after 5-10 seconds of cranking. It acts a bit like a flooded carbureted engine. Once started it runs smoothly and it has a steady 18 hg of vacuum at idle. Timing is 12° advanced. Is starting being affected by the fact that the MAF is so much smaller than the throttle body?
 
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If the MAF is working properly it doen't care about the size of the throttle body.

Dump codes sticky

Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
 
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Thanks, guys. Since my original post, the engine has gone from hard start to no start. I will check out both items. If the TFI is bad will it show as no spark from the coil to the distributor and/or distributor to plugs?
 
jrichker, if I understand your code dumping process, I can’t do it if the engine won’t start. Is the concept that a bunch of stored error codes may interrupt normal computer operation during start? I have a spare computer but would not want to put it in and mess it up too. Thanks.
 
Thanks, guys. Since my original post, the engine has gone from hard start to no start. I will check out both items. If the TFI is bad will it show as no spark from the coil to the distributor and/or distributor to plugs?


Cranks OK, but No Start Checklist for Fuel Injected 5.0 Mustangs model years 1986-1995

A word about this checklist before you start: it is arranged in a specific order to put the most likely failure items first. That will save you time, energy and money. Start at the top of the list and work your way down. Jumping around will possibly cause you to miss just what you need to see to find and fix the problem. Don’t skip any steps because the next step depends on the last step working correctly.

Revised 26-Jul-2017 to add fuse link diagram.

All text applies to all models unless stated otherwise.

Note: 94-95 specific changes are in red

1.) Remove push on connector (small red/blue wire) from starter solenoid and turn ignition switch to the Run position. Place car in neutral or Park and set the parking brake. Remove the coil wire from distributor & and hold it 3/8” away from the engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.

Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.

No spark, possible failed items in order of their probability:
A.) MSD, Crane, or other ignition box if present - Bypass it and return to stock configuration if possible. Do this as a temporary measure to eliminate it as a possible problem source.
B.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors. A failing PIP sensor will sometimes let the engine start if the SPOUT is removed. See paragraph 5A – Using a noid light will tell if the PIP is working by flashing when the engine is cranking.
C.) TFI module: use a test light to check the TFI module. Place one lead of the test light on the red/green wire on the ignition coil connector and the other lead on the dark green/yellow wire on the ignition coil connector. If the TFI is working properly, the test light will flash when the engine is cranked using the ignition switch.
D.) Coil
E.) No EEC or computer power - EEC or computer relay failure
86-93 models only: EEC relay next to computer - look for 12 volts at the fuel injector red wires.
94-95 models only: EEC or PCM power relay in the constant control relay module. Look for 12 volts at the fuel injector red wires.
Both 86-93 and 94-95 models: No 12 volts with the ignition switch in the run position on the fuel injector red wires. The relay has failed or there is no power coming from the ignition switch. Make sure that there is 12 volts on the red/green wire on the coil before replacing the relay.
F.) No EEC or computer power - fuse or fuse link failure
86-93 models only: Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid. Look for a 20 gauge blue fuse link connected to 2 black/orange 14 gauge wires.
94-95 models only: 20 amp EEC fuse in the engine compartment fuse box. Look for 12 volts at the fuel injector red wires.
G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire. No 12 volts, blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire on the ignition switch with it in the Run position. No 12 volts and the ignition switch is faulty. If 12 volts is present in the Run position at the ignition switch but not at the coil, then the fuse or fuse link is blown.
Note: fuses or fuse links blow for a reason. Don’t replace either a fuse or fuse link with one with a larger rating than stock. Doing so invites an electrical fire.
Ignition fuse links may be replaced with an inline fuse holder and 5 amp fuse for troubleshooting purposes.
94-95 models only: Check inside fuse panel for fuse #18 blown – 20 amp fuse
H.) Missing or loose computer power ground. The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness
I.) Computer. Don’t replace the computer just because you don’t understand how it works. Computers seldom fail, it usually is a sensor or wiring problem that causes the problems.
J.) Bad or missing secondary power ground. It is located between the back of the intake manifold and the driver's side firewall. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges.
K.) Engine fires briefly, but dies immediately when the key is released to the Run position. Crank the engine & when it fires off, pull the small push on connector (red/blue wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. Good 12 volts, then replace the TFI.
See the Ignition switch wiring diagram for more information on the ignition wiring fuse link because it is the next thing to be tested. You will need a Multimeter or DVM and know how to use the Ohms function to check continuity between the red/green wire on the ignition coil and the red/green wire on the ignition switch. Make sure that the ignition switch is in the off position when you do the check. You should see less than 1 Ω (Ohm) between the red/green wire on the coil and the red/green wire on the ignition switch. More than 1 Ω means that the fuse link may have blown open and needs to be replaced. If you get 1 Ω or less means the fuse link is OK and the ignition switch is bad.

Wiring Diagrams:
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Engine Information Everyone should bookmark this site.


Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 94-95 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

AutoZone wiring diagrams: You can navigate to the diagrams yourself via Repair Info | AutoZone.com and select the car year, make, model and engine. That will enable you to bring up the wiring diagram for your particular car.

2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability: [/b]
A.) Moisture inside distributor – remove cap, dry off & spray with WD40
B.) Distributor cap
C.) Rotor
D.) Spark Plug wires
E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

3.) Spark at spark plug, but no start.
Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.

Two reasons:
1.) If it backfires, the chance for a serious fire is increased.
2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.

If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 2-4 seconds and shut off. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.

attachments\68357


If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the Schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In a pinch, you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have. If you have any doubts about having sufficient fuel flow/pressure, rent a fuel pressure test gauge from the auto parts store. That will tell you for sure if you have adequate fuel pressure.

4.) No fuel pressure, possible failed items in order of their probability:

A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
C.) Clogged fuel filter
D.) Failed fuel pump

E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.

The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.



64326.gif




94-95 models only: 20 amp fuel pump fuse in the engine compartment fuse box. Look for 12 volts at the Dark green/yellow wire on the constant control relay module.

F.) Engine seem to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.

5.) Fuel pressure OK, the injectors are not firing.
A.) The PIP sensor in the distributor tells the computer when to fire the injectors. A failing PIP sensor will sometimes let the engine start if the SPOUT is removed.
A noid light available from any auto parts store, is one way to test the injector circuit to see if the injectors are firing. The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and try to start the engine: it will flash if the injector is firing.
I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
B.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
C.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).

See the graphic for the 10 pin connector circuit layout.
attachments\610738


The injector power pin is the VPWR pin in the black 10 pin connector.

D.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the EEC relay and the red wire for the 10 pin connectors.
E.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe the black/white and green wires to measure the TPS voltage.

On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage.

It should be .5-.1.0 volts with the key on, engine not running. Note that if the black/white wire (signal ground) has a bad connection, you will get some strange readings. Make a second measurement using the battery post as the ground to eliminate any ground problems. If the readings are different by more than 5%, you may have a high resistance condition in the black/white signal ground circuit.

6.) Spark & fuel pressure OK.
A.) Failed IAB or improperly set base idle (no airflow to start engine). Press the throttle ¼ way down and try to start the car. See the "Surging Idle Checklist for help with all your idle/stall problems.
B.) Failed computer (not very likely)
C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently. If you removed the distributor, there is a good probability that you installed it 180 degrees out of time.
D.) Firing order off: HO & 351 use a different firing order from the non HO engines.

HO & 351W 1-3-7-2-6-5-4-8

Non HO 1-5-4-2-6-3-7-8

E.) No start when hot - Press the throttle to the floor & try starting it, if you get this far. If it starts, replace the ECT.

F. ) Engine that has had the heads off or valves adjusted. Do a compression test to make sure the valves are not adjusted too tight. You should have a minimum of 90 PSI on a cold engine.
 
I have gone through jrichker’s no start checklist. I have spark from the distributor and fuel at schrader valve as well as strong odor from pipes and plugs after cranking. Timing is good because engine was running and a known good spare computer didn’t help. Ran KOEO codes and got 19,69, and 6. Regarding code 19, I have power at pins 37/57 to fuel pump which primes, and injectors. One website says code 19 is “electronic ignition cylinder id sensor/circuit problem – ignition systems”. Don’t know what the code 6 means. ACT sensor is new and ECT correctly inputs to dash gauge. Should I replace the distributor to correct cylinder id issue?
 
Code 19 - Engine off - No Vehicle Power (pins 37 + 57) or bad PCM VPWR

Revised 30 Mar 2019 to add computer wiring connector diagrams.

Diagnosis: This is a wiring problem that is from a bad ECC power relay, bad connection, bad fuse link, bad ignition switch or a bad computer. The ECC relay is located on top of the computer under the passenger side kick panel. Pull the connector off any fuel injector and measure the voltage on the red wire: if its 12 volts or better, the ECC relay is OK. If the ECC relay is OK, pull the kick panel off and measure the voltage at computer pins 37 & 57. If it is 12 volts or more, then the computer's diagnostic firmware has taken a dump and is defective.

Computer wiring harness connector, wire side
71316.gif


Computer wiring harness connector, computer side
88243.gif



Engine running - Erratic idle during test (reset throttle & retest) - Idle Set Procedures .
See http://www.stangnet.com/mustang-forums/698148-help-me-create-surging-idle-checklist.html#post6855020 for the best way to set the mechanical base idle and cleaning procedure for the IAC/IAB.

Code 6 is a flakey thing that is present when the engine running codes start to dump. It is supposed to be the engine number of cylinders code, but some perfectly normal Mustangs will spit out 6 instead of 4 or 8.

Code 69 is a fault with the AODE automatic transmission in 94 and 95 V8 cars.
 
Thanks, jrichker. With ignition on I have 12 volts at injector #5 and 12 volts at both computer pins 37 and 57. Fuel pump primes each time ignition engaged. I disconnected computer and connected into known good spare computer I had rebuilt to replace caps and which successfully operated car after rebuild. Still no start. I reconnected back to computer in car and checked for codes before and after cranking. Got 12 and 2 both times. 19, 69 and 6 are gone after the disconnect. What do you suggest I try next?
 
Well, I’m stuck. Today, I:

Rechecked for spark between distributor and spark plug - ok
Checked for injector #5 pulse with noid light -ok
Rechecked grounds at computer pins 16,20,40,46,60 -ok
Installed new distributor - no start
Checked coil resistances -ok
Sprayed ether into intake - no engine response
Connected known good spare computer - no start

I must be missing something that initially caused a hard start, but smooth running after three hard starts until turned off with key, and then a no start, not even a single cylinder firing during several second cranks with spark and strong fuel odor at pipes. Is there a sensor on the car that would cause a no start?
I appreciate any suggestions, guys! Help!
 
Thanks so much, Karthief. I have jrichkers no start checklist printed out on my workbench. When I follow it, I get to timing or computer since I have spark and fuel and injector pulse. I have reset timing multiple times using jrichker method of finger on spark plug #1 hole, cranking to compression, wrenching to tdc and rotor at 12 o’clock. My spare computer is one I bought and had rebuilt last year and was in the car working last October. Could some sort of wiring issue be killing my computers?
 
Putting the rotor at 12 oclock is a relative term, when your pointer is at tdc your rotor should be at or very near the #1 spark plug wire.
don't over think things.
if you spray either and it will not start that indicates a no spark situation but if your timing is WAY off it also will not start.
Basics. Check firing order, make sure you are not 180° off and the rotor is at or near the #1 plug wire with the pointer at tdc.
Note: if the balancer is bad the outside ring may have rotated throwing your marks off.
I marked the out side of the distributor where the #1 plug wire is. Note fuel pressure. I start with checking spark at the plug, then the coil.
you have to be methodical in your diagnostics.
 
All good points. I actually have been more methodical than my notes imply. Just getting really frustrated and keep trying the same things over and over.
Rotor tip is positioned under the #1 spark plug wire terminal of the cap when pointer at tdc. What would cause balancer to slip? I have been wrenching engine in clockwise direction looking from front to rear when positioning balancer with pointer. Is that a left handed thread and I am loosening? I have tried rotating the distributor back and forth to its limits while cranking with no response. I have even intentionally inserted the distributor 180° off and tried to start. I have checked spark with an inline spark tester between the coil and distributor, between the distributor and the #1 cylinder and have pulled a plug and observed it to spark when grounded to engine. Even though presence of spark says ignition not problem I have verified correct voltages and resistances at the 6 TFI connector terminals using a combination of a jrichker check list for pip diagnosis and my Chilton’s manual.
Enough venting. I will get a tester and measure fuel pressure at crank and also plan on measuring compressions, the third thing I need to fire. How do I check the balancer position? Is there a way to check my computers other than sending them out for diag?
Thanks again for your help.
 
The no start checklist should cover this issue.
If the rotor is at or near the #1 plug wire location on the distributor with the balancer at the tdc mark with the piston at the top of the compression stroke then your balancer is likely ok.
The outer ring of the balancer is press fit with rubber between the ring and hub that bolts to the crank snout, time and heat hardens that rubber and the balancer ring will become loose enough to wobble and even slip on the hub.