95 Ranger 4.0

My problem started two years ago when my truck wouldn't start the mechanic found it was the ground for the ECM and away I went. Recently the truck is exhibiting the same symptoms.

1) Check engine light not coming on when key is turned resulting in not starting.

I have cleaned off the ground area, the bolt and greased everything up to help make better contact. Here is what is happening when I turn the key the check engine light sometimes comes on and sometimes it doesn't. Sometimes I have to wait a few seconds and then it comes on. Yesterday however the truck wouldn't start and I checked the voltage from the battery to the ground screw for the ECM and it was 12.55 volts. After a few minutes of being in the on position the check engine light came on the fuel pump primed and I was able to start it up and come home.

I am wondering what I can check and or do to ensure that this will stop. The worst part is that the problem is intermitent. Any and all ideas will be appreciated!

 

What year/engine of truck? and when you greased up what kind of grease?
Dave

 

I used a thick battery terminal grease on the ground screws.

 

Would I want to measure the dc current or resistance? If so could you help me out in how I would want to do that with my multimeter. I know it can do this I am just now sure how, I have only ever used it to take voltage readings.

 

Most grease is an insulator, So that might be a problem. I don’t understand about the dc current or resistance. What engine and what year is you truck?
Dave

 

Try making up a good quality ground jumper lead, as a test device. Make a good connection to the computer & chassis. If the problem goes away, you'll know the computer ground is somehow faulty.

 

Dave, I don't think this grease is an insulator it is a battery terminal grease used to keep corosion away. The truck is a 95 Ranger 4.0 I was interested in checking the resistance in the wire and the dc current with my multimeter. I just wasn't sure how I could go about that.

 

Getting into how to use a multimeter is a little more then I would want to get into in this forum. There are a couple of relays that could be causing your problem. The fuel pump relay and the PCM power relay may be intermittent. There are lots of other connectors, grounds, etc that could cause it. But the relays are cheap and are prone to fail intermittently. I re-read your post and saw you posted the year and engine in it. Sorry, the old attention span isn’t what it use to be.
Dave

 

Is there a way I can test the relay's? It maybe the PCM relay but I am pretty sure it cannot be the Fuel Pump relay. The fuel pump waits for the PCM to power up and that is where my problem is. My problem is involving the PCM somehow and someway because when I turn the key the check engine light isn't turning on. As soon as it does (instantly, 5-10 seconds later, or 3 minutes later) the fuel pump relay kicks on and the fuel pump primes.

 

Well you could try tapping lightly on the relay when it won't start. Or maybe swapping the pcm relay with another relay that won't affect the truck starting.
Dave

 

relays are easy:

1) set the multimeter to 2000 ohm resistance, or the audiable one for diodes whichever you want (your testing for continuity.. is it beeps, its like a good connected wire between the leads) you should see an arrow with a vertical line in front of it... possibly some round lookin lines around it that look like ripples in a pond? thats the setting.

2) identify, locate and pull the relay in question. This is important, cause if you dont know what your pulling, you got problems buddy.

3)look at the blades/markings. a relay is a two part device 1 is an electromagnet (you know the hunk of iron with wire wrapped around it? hook the ends to a battery and you can pick up nails with it until you kill the charge?) the other end is a simple switch, that either disconnects or connects depending if the magnet coil is charged, or the setup of the relay. 2 leads should give you a few ohms like 2 or 3 or even 5ohm.... thats the coil. it should not be 0. The coil should show some resistance at the lowest setting of your meter. if not, it could be fused (bad).

the other two are either connected or not connected. if you get more than 3-4 ohms on those connections, you got a problem. To determine if the switch is stuck, look and see if you see N.O. (nomally open - means normally off) or N.C. (nomarlly closed - means normally on). On give you a few ohms or even 0 or a beep, off, nothing. This is a simple continuity test (resistance).

If you have the relay in the powerbox, put your finger on one and get someone to key the engine. You'll feel the click if its working right, but the contacts may be screwed, so check if it is delivering power. No click, no action, replace, after you KNOW that its getting power anyways (thats to the coil, and to the source lead) . Tapping is a great idea for locating the problem, but will not solve it unless the major connections to the relay have been inspected for corrosion and intermettincy as well. It is good practice for one not to always assume that the contacts have fused toghether/apart without properly ruling out anything else that could cause the issue. Ahrkams Razor, my friend. I have a friend who went through 5 $20 relays and it was the blade connectors that was giving him the issues. Couldn't see it unless he took that box apart, so always confirm for power/ good solid connection with your meter.

Also, if you put the meter on volts, over 12 (so 20 would work), DC, (NOT AC) put one on the + post of the battery, and poke around until the relays/fuel pump click again, or when you dont get 12v where there should be a ground. This includes block, bolts, chassies, and any ground wire.

You can also use the same 2000 ohm resistance setting, keep one on the - post and poke that way while keyed, looking for 3ohm or less. If not, theres a bad ground too. Be sure not to touch hot (+) wires while in resistance, and connected to ground on the other end. Bad. You gotta do this test live sometimes cause you can get the situation that a relay kills a ground connection too... you just never know unless you have/know the schems. Assumptions can be the mother of all screwups.

By the way, when using volts, red is +, black is -. Do not measure dc current. You have no use for that with this problem. That involves putting the meter in the right setting, and putting the leads of the meter in series with the circuit, and most meters can't handle more than 10 amps unfused. Nevertheless this is not necessary in with your problem, and I wouldn't do it unless you knew what you are doing, cause I can guarantee you that you can easily make a mess that way.

Use the pinpoint test availble from the stickies, follow everthing you can find, confirm everthing, assume nothing, and your truck will run again. Be careful, but most of all, Have Fun!

Good luck

 

Thanks so much for the insight, I will give it all a try. I appreciate the tutorial in relays. I knew a little about them but this helps a lot.