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88 strange no start

skyaugen

NAXJA Forum User
Location
new jersey
First I would like to thank everyone who help me solve my first two no start

problems 4 months ago - a bad cps and bad starter relay.

This time when I try to start and it's cranking, I looked at my battery gauge and

the needle just goes to the top of the red zone and not the usual middle and

starts going down. I figured my battery was bad but had it checked at two

places and they said it was fine. What should I check for to solve this?
 
For any no-start, the troubleshooting strategy is basically the same. Finding out what part of the starting equation you are missing.....fuel or spark. I'd focus on that rather than your battery gauge at this stage.

Do you hear the fuel pump energize and run for a couple of seconds when the key is turned to the ON position? There are two quick and dirty things you can do to help isolate this.

1. Spray a small amount of starting fluid into the intake. If the engine starts and runs momentarily, you have a fuel delivery problem, not an ignition (spark) problem. Fuel pressure testing at the schrader valve on the fuel rail can help you isolate fuel delivery problems.

2. To verify spark, remove a spark plug, keep it hooked up to the plug wire. Place the spark plug electrode near a good engine ground. Have a buddy crank the engine while you watch for spark. You are looking for a strong, blue, snapping spark. Yellow/orange means a weak spark which may not be strong enough to start your engine.

Once you know whether you're missing fuel, spark or both, the list of usual suspects gets a whole lot shorter....post back what you find.
 
For any no-start, the troubleshooting strategy is basically the same. Finding out what part of the starting equation you are missing.....fuel or spark. I'd focus on that rather than your battery gauge at this stage.

Do you hear the fuel pump energize and run for a couple of seconds when the key is turned to the ON position? There are two quick and dirty things you can do to help isolate this.

1. Spray a small amount of starting fluid into the intake. If the engine starts and runs momentarily, you have a fuel delivery problem, not an ignition (spark) problem. Fuel pressure testing at the schrader valve on the fuel rail can help you isolate fuel delivery problems.

2. To verify spark, remove a spark plug, keep it hooked up to the plug wire. Place the spark plug electrode near a good engine ground. Have a buddy crank the engine while you watch for spark. You are looking for a strong, blue, snapping spark. Yellow/orange means a weak spark which may not be strong enough to start your engine.

Once you know whether you're missing fuel, spark or both, the list of usual suspects gets a whole lot shorter....post back what you find.

X2 Yes this should tell ya..

Good Luck
Nick
 
I just checked the fuel pump and it's working but I'm not getting any spark.

Also it's a weaker cranking when trying to start it up.
 
Also it's a weaker cranking when trying to start it up.


Fix the battery problem. If its cranking too slow and/or the voltage is getting pulled down too far, it will not fire up. Make sure the battery connections are clean and solid as well. Throw a set of jumper cables over to another running vehicle to see if that helps.. What year was this, btw?
 
The fact that it's weaker cranking when trying to start it probably means that the battery is down because of extended cranking intervals without charging.....you said you already had the battery load tested so put a battery charger on it for a while. Gotta have a strong electrical system to fire the engine.

How did you verify no spark? If you have no spark, the two things I'd check first would be the crankshaft position sensor and the coil, starting with the crank sensor. Here's some testing information on your vintage
---------------------------------------------------

Crankshaft Position Sensor: Common Symptoms if bad:

*Both the fuel gauge and or voltage gauge may not work/display

*You will have no spark. Fuel pressure may check okay but fuel won’t get to injectors

*Crank sensors can be intermittent; "thermal failure" is pretty common. Means that the sensor fails when engine gets hot, but works again when cooled back down. Be aware of this when testing as if you have a sensor that suffers from thermal failure, it will probably test GOOD as soon as it cools down.
--------------------------------------------------------------------


CPS TESTING PROCECURE for 1987 – 1990 4.0 L engines

Test # 1

Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.


Test # 2

You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.
 
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