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reesa
Dodge Dakota
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8/20/2003
08:47:46
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 Subject: RE: Help! Truck won't start!
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JKnPA was right. It's not the fuel pump.
We checked the splice "S115" it did have some build up on it, we cleaned it. The fuel pump is getting power. He checked it with the test light. But he said the light was pretty faint. Could be maybe because the battery is just about drained? He said the grounds are good. The fuse in the PDC box looks good. The relays look good. The only thing I can think happened is the fuel pump worked before he changed the distributor cap and magnetic pick up. There's a wire that comes off the magnetic pick up. Could that be the culprit. Do you know where that eventually ends up? When he changed the coil the fuel pump was still working. So I don't think it has to do with the coil. But I could be wrong. I'm thinking maybe when he lifted the distributor cap to change it something came loose. It's a pretty tight squeeze to get in and out of there. What do you think?
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reesa
Dodge Dakota
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8/20/2003
11:30:50
|  RE: Help! Truck won't start!
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Ok another question if spark plug wires were'nt put on in the correct firing order would that prevent fuel pump from kicking on as some type of fail safe?
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whitedakota2
Dodge Dakota
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8/20/2003
12:43:51
| RE: Help! Truck won't start!
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Back to the basics, if you turn on the key and the pump doesn't run, then you have a problem. The pump is activated during the first turn of the key when the ASD circuit is forced on. After that it won't run again unless the ASD circuit is active. The ASD circuit will not activate after the first turn of the key unless it detects the motor is running. So to get past the first problem you need to find out why the pump does not run when you turn on the key. This could be because you have a low or bad battery. You must have good power to start the truck. Check through things again before going on to other parts of the truck. You may cause more problems than you have now.
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reesa
Dodge Dakota
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8/20/2003
14:40:35
| RE: Help! Truck won't start!
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We tried jumping truck and pump still didn't kick on. You think maybe I should try switching batteries with my van (which I know is good) and see if pump kicks on?
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JKnPA
Dodge Dakota
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8/20/2003
15:51:45
| RE: Help! Truck won't start!
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Reesa........
You need a "good battery".....as WD2 said. Use a good battery.......and go from there. I use a 'muti-meter' (volt/ohmmeter) when troubleshooting......because I want to know the exact value of what I'm reading.
Don't know about the 'mis-wiring' of the spark plugs......most likely it will not start; verify the wiring is correct.
* As you stated in your original post.......
"the ASD relay must receive a tachometer signal from the distributor in order for the fuel pump power circuit to be energized". So trace that wire and verify continuity( ohmmeter). That wire may go to pin 51( ASD relay) of PCM...see bottom of pg.12-31...... shuts off relays...I think!
* can you get a fuel pressure reading?? Book says (1994) between 35-45 psi.
*** see haynes manual pgs. 4-1, 4-3.
hang in there......
JK
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whitedakota2
Dodge Dakota
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8/20/2003
16:21:51
| RE: Help! Truck won't start!
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The statement "the ASD relay must receive a tachometer signal from the distributor in order for the fuel pump power circuit to be energized" is true for the truck to run but the ASD circuit is activated on the first turn of the key for a few seconds so the pump runs to prime the fuel system. If the pump does not run during this time, you have a problem in the pump circuit or the pump.
Of course there could be something wrong with the PCM but I am hoping for the easy, cheaper fix. :)
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JKnPA
Dodge Dakota
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8/20/2003
17:06:42
| RE: Help! Truck won't start!
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WD2.....
No one said you were wrong.
We both agree.....you need a 'good battery".
*When I start my truck...... I never hear the fuel pump running.....perhaps its my hearing!
* if the feedback signal ( from the tach) is open .....will the truck start and then stall? I don't know..... I'm not an auto tech. I'm giving Reesa ideas where to look.
* I think Bill had a good idea to check the fuel pump pressure......just trying to help.
Why.......because tomorrow I may have the same problem and I may need help.
best wishes....
JK
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reesa
Dodge Dakota
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8/20/2003
19:14:18
| RE: Help! Truck won't start!
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We changed the fuel pump yesterday, and it still doesn't kick on. We tried swapping batteries and that still didn't help. I'm gonna see if we can borrow a ohm meter tommorow. I'll let you know what happens! Thanks Again!
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JKnPA
Dodge Dakota
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8/20/2003
21:53:49
| RE: Help! Truck won't start!
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Reesa......
OK......but you still need a good battery. I still suspect you have a bad connection, splice, or fusable link giving you an 'open" circuit. I think you can 'jump" the 12v. to the fuel pump to see if it cycles. If it cycles....then you know the problem is in the circuitry before the "jump-in" point.
Ric6312.....
"The fuel pump goes bad 99% of the time???
Still waiting for the manual that shows a "back-up relay".......didn't see it in my Haynes manual. Perhaps Haynes made a mistake!
Jk
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BillH
Dodge Dakota
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8/21/2003
07:58:15
| RE: Help! Truck won't start!
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Just a point of interest regarding a possible back-up relay. I checked the wiring diagrams in both my Mitchell and my Haynes manuals and could find no back-up relay.
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JKnPA
Dodge Dakota
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8/21/2003
09:39:46
| RE: Help! Truck won't start!
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Bill,
I don't think there is a 'back-up'relay.
This guy recommends just replacing the fuel pump without checking anything else......right!
I think Reesa will find an "open" circuit somewhere or bad connection....."bad grounds" are sometimes hard to find!
JK.
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BillH
Dodge Dakota
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8/21/2003
13:49:14
| RE: Help! Truck won't start!
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JKnPA. I agree, I too don't feel there is a backup relay. I just wanted to share my findings. I also concur that with the first turn of the key the fuel pump energizes for about 1-2 seconds and then the ASD kicks in to shut it down. In that first few seconds my fuel pressure guage quickly comes up to pressure clearly indicating if the pump is working. I ended up with a bad fuel pump but I too was not going to change it until I was very sure that the circuitry was working correctly. In the quest I found that the large square connector on my firewall had been getting water into it and had caused a high-resistive short in my fuel pump circuit which is why I prefer a multimeter over a test light. That's when I decided to visually check/verify the entire circuit. The extra effort paid off. Hope this helps.
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JKnPA
Dodge Dakota
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8/21/2003
15:34:16
| RE: Help! Truck won't start!
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Bill............ I agree. Corroded connectors can be a 'nightmare".
Since you have the Mitchell Service manual, does it explain the operation of the ECM system......like the ASD & fuel pump relays?
Looking at the elec.schematic....it sems to me both relays are energized and stay energized as long as there is a "ground" (0) on the lower side of the relays(pin 51 of PCM). If this signal(ASD relay) goes "high"(12v.) both relays will shutdown. This may be the signal from the "tach" or cam sensor which shuts the fuel pump off because of no spark.
Since I don't have a detailed ECM manual, I'm theorizing.
Any thoughts....
JK.
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Billy Woodall
Dodge Dakota
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8/21/2003
21:09:20
|  RE: Help! Truck won't start!
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I like to drive my truck really fast with heavy acceleration a lot. After I would finish driving and turn off the vehicle, I would try to start it again but it won't start. Sometimes is sounds like it gets close to starting, but it dies again. I have to wait extended periods of time to get it to start again (30 minutes to an hour or so). It turns on easily after the truck has been "resting" for a while, but not after driving it. I thought my fast driving was the problem and it maybe affected the fuel pressure regulator, but even when i drive slow it still happens. I replaced my old battery with a brand new one and it still continues. The spark plugs are new and the starter is new. Do you think it is the fuel pump regulator, some eletrical circuit damage, or something else?
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BillH
Dodge Dakota
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8/22/2003
08:00:04
| RE: Help! Truck won't start!
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JKnPA. The Mitchell manual does not go into the specific logic operations of the PCM but you are correct in that both the ASD and Fuel Pump relays get their "control" ground from pin 51 of the PCM. The control circuit for both relays is ganged together and they receive their 12V from the ignition. I have been able to conclude that the PCM must receive a signal from the camshaft position sensor (in distributor) and the crankshaft position sensor in order for the PCM logic to provide a ground at pin 51 for the two relays to work. It does provide that ground for the first 1-2 seconds that the ignition is turned on but if it doesn't receive those other inputs then its internal logic will deny the ground path for the relays thereby activating the ASD circuit. When I was troubleshooting my fuel pump problem I found it necessary to isolate the fuel pump circuit from the PCM so I could tell if the pump was bad or the problem was from the PCM/sensors. By removing the fuel pump relay and jumping the red/wht and grn/blk wires I was able to control the fuel pump operation manually and effectively bypassed the control circuitry and was able to isolate my fuel pump problem.
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JKnPA
Dodge Dakota
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8/22/2003
14:11:27
| RE: Help! Truck won't start!
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Bill....
Thank you again.
I thought that is what is happening. I wanted to tell Reesa to do what you did.....namely "jump the 12v." to the fuel pump at the output of the fuel pump relay. That would check the wiring to the pump and the pump without the truck even running. I saw that at a Toyota site, which I will give you the link.
This is a Toyota site.....i like it because its free and explains the basic operation of ECM operations. I use it because I have no 'exact Dodge manual" and it gives me a general idea how things work.....thank you.
I'm still looking for a 96 "factory service manual" and a "ECM manual" for my 96 dakota.........anyone know where I can get one???
Link...... @ basic ECM operations......
http://autoshop101.com/
JK.....
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reesa
Dodge Dakota
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8/24/2003
15:21:22
| RE: Help! Truck won't start!
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Hi! Put the new fuel pump in, still getting a dim light on the test light on the light blue and yellow wire that connects to the fuel pump. Then he went up to the magnetic pick up and he's getting no light at all at the plug that comes out of the wire harness that you plug the magnetic pick up into. What would be the next step to check.
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BillH
Dodge Dakota
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8/24/2003
23:30:07
| RE: Help! Truck won't start!
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reesa. The blue and yellow wire have nothing to do with the pump. That wire is for the fuel guage sensing circuit. The green & black wire is the one that delivers 12 volts to the pump. Do you have voltage to that point? Before I would start looking at the camshaft sensor in the distributor, I would make very certain that the fuel pump is now operating properly. (See my post a few days ago on how to manually energize the fuel pump.) Once you hear that fuel pump running, only then would I start looking at other areas. Hope this helps.
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reesa
Dodge Dakota
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8/25/2003
05:16:19
| RE: Help! Truck won't start!
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Thanks Bill. Could you explain exactly how to jump the red/wht and grn/blk wires? He's not really sure how to do it and afraid he may do more damage. Thanks Again! Reesa
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JKnPA
Dodge Dakota
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8/25/2003
07:07:29
| RE: Help! Truck won't start!
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Reesa... leave the key..... OFF.
The easiest place to 'jump-in" the 12v. for the fuel pump is at the fuel pump relay in the PDC box. Remove the relay. There s/b 12v. on pin 30 .......all the time. It is labeled pin "B" (A14) on sheet 12-31 of the Haynes manual.You will be jumping pin 30 to pin 87. Pin 87 is labeled "D" in the wiring diagram(schematic) and goes to the fuel pump.
Verify you have 12v. on pin 30. When you jump pins 30 & 87.......just for about 2 or 3 sec., you should hear the pump cycle. You need two people to do this. If you don't hear the pump cycle.......you have an "open" circuit between the relay and the pump. You need an ohmmeter to find the open circuit.
Your jumper wire s/b larger than #16 gague wire.......#14 elec. wire would be good.
This is a link to the toyota technical site........see " understanding relays and questions" near bottom of the page. Sheet 9 0f 20 shows the ISO relay we are using. Pins 30& 87 are the contact pins. Pins 85&86 are the coil pins.
http://autoshop101.com/
JK.
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reesa
Dodge Dakota
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8/25/2003
08:18:46
| RE: Help! Truck won't start!
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Ok I think I got it...I make sure the key is off :) Then I take out the fuel pump relay. The top pin hole would be pin 87 and the bottom would be pin 30. Then we take a piece of wire and put one end in pin 87 and the other end in pin 30 for a few seconds. Do I turn the key on at this point?
He checked pin 30 the other day and said there was no power to it at all. Should it be at 12V even with the key off?
We will try it as soon as he comes home and let you know what happens. We'll test the 30 pin for 12V again too. I want to make sure I understand it right before we try it so I'll wait for your reply.
Thanks Again!
I don't want to leave this out just in case it may help figure out what's happening...he said the other day that when he changed the magnetic pick up he had to pull up on the wire harness that's on the back wall to get at the plug for the magnetic pick up.
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reesa
Dodge Dakota
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8/25/2003
08:22:30
| RE: Help! Truck won't start!
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I forgot to say we got a multi meter. When checking for 12V at the 30 pin where do I put the black end and the red end. Sorry for so many questions! I never used a ohm or multi meter. Thanks Again!
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JKnPA
Dodge Dakota
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8/25/2003
08:47:48
| RE: Help! Truck won't start!
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Reesa....... Leave the key.. OFF....for the entire test.
You MUST have 12v. at pin 30...always.
Measure between pin 30 and "ground". Use the "negative" terminal of the battery as ground. You can use the light to check for 12v. Before using the 'multi-meter........read the directions!
Check the light/voltmeter by reading the voltage across the battery........OK
Were you able to get to the website I gave you??? You need Acrobat Reader to open the file......it takes about 2min. to download/open the file on relays....
This test just puts the 12v. on the fuel pump......without using the key!
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J and J Auto
Dodge Dakota
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8/25/2003
09:02:59
| RE: Help! Truck won't start!
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what year is this truck and do you still have
spark when cranking.
Take the wire off the dist cap hold it near a good
ground and have someone turn it over and check.
off the cap not the coil.
If no spark or fuel you may have a famous prob
that happens, about a foot behind the power dist
box under the hood drivers side in the wire
harnas there is a red feder wire going to 3 wire's
that has a connection that caroads and loses
contact and you will have no power to the PCM no
spark and no fuel. But it will still turn over
You need to untape the harnas find this wire and
fix the connection by removing the old connector
and either solder or put new connectors on.
Larry
J&J Auto
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reesa
Dodge Dakota
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8/25/2003
09:16:02
| RE: Help! Truck won't start!
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I don't have the directions for the multi meter it's used. I did look at the website. I'm gonna read it over now. I tried to get the directions for the multi meter online but the manufacturers website didn't have any. Sorry for making you repeat everything. Ok, Thanks again.
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JKnPA
Dodge Dakota
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8/25/2003
12:16:52
| RE: Help! Truck won't start!
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Reesa..... If you have time use the "light" to check the voltage at pin 30. Verify the light works by checking the battery. If you don't have the 12v. on that pin 30.......you have an "open" going to that pin. Somewhere that wire goes back to the battery........it may be that "S115" splice that I mentioned earlier.
Don't use the muti-meter until you read the directions.......its easy to blow the fuse inside the meter.
I think you probably have a 'bad connection", maybe a 'ground wire, or the 12v. wire. This is why you check wiring connections before you buy $150 parts.
Jk.........keep the faith
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