1998 dodge 3.9 ign

LynnM

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#1
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MAKE: Dodge
MODEL: Ram Van
YEAR
:1998
MILES:140K
ENGINE
:3.9
DESCRIBE ISSUE.... running very poorly, will barely run. Have been having ign problems with P351 ign failure.. Was saving for a new computer. Last time was running and it quit had to recycle the key off then back on , it started like usual. Was on the freeway and going down the road and the truck made a loud backfire and then made some other noise ? I thought it might be the fan ??? Towed it home checked the timing chain, installed new computer, some other needed maintenance.. Still barley runs. Could I have blown the intake plenum or the converter/exhaust?? Any ideas
Previously replaced the coil & coil HT wire
 
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#2
You did use a scanner -only code is p0351? Key dance trick and code readers are limited.
this is a single coil - and has distributor... this is @ change year to multi coils. just making sure I on right eng.
As the PCM controls the coil-
Have you changed coil? inspected cap and rotor?

you have NOT moved dist? moving this does NOT time the engine - and I suspect the issue.

oops I just saw the changed coil and 2nd wire...
 

nickb2

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#4
If over 2.0 ohms, repair short to ground.

Another trick, you could swap to a MSD ignition kit for the price of that PCM. But that is a big upgrade.

Try this link out. You may find bullet proof stuff here. http://www.jegs.com/vct/MSD/121/1010359

I also read that you replaced the PCM, did you get the software upgrade or did you just get it from a scrapyard. You will need release version 21 or higher. You will need a DRB3 for that software upgrade. Unless you have a J2534 interface.

I hope those snapshots were not to fuzzy, but all wiring is there. That specific MSD coil for your 3.9 looks solid and most likely worth it if this is going to still be a daily driver. The ignition module fits almost any car truck of that era and worked great for me on the track. Also the dizzy looks rock solid.

Anyway, I do not want to talk your ears off, but that MSD is a good viable option to your solution.

Cuz if it is only a PCM driver issue, why replace the PCM.

So now I am just throwing ideas out there.
 
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#5
I really misread the post before. I confused speculation guessing with actual and now unsure if P0351 is still there. Why did you condemn computer? Must have
a reason to suspect it...


Have you done BASICS-
What codes are you now seeing?
spark at several plugs?
Fuel pressure?
Noid light?
Vacuum reading?
compression test?
 

nickb2

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#6
kev2, right zith you there:

I hqte ,y keybqrd right noz: I think it zent to ger,qn or so,ething:

Everyti,e I pqss ,y keyboqrd to ,y GF I get this shyte:

The lqst one I bent over ,y knee:

I zill need q nez keyborqd qnd suck it up:

I q, trying for the english clqssic for,; nothing zorking; I think I q, zriting in szedish or so,e other lqnguqge: ?ight qs zell try to speek greek like ,y GF:

Ok; enuff; shutting dozn before I get pissed offed qnd breqk so,ething else:
 

nickb2

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#9
If I could eqt PC s qnd ,other boqrds qnd the ,ouse thqt cq,e zith: ,y teeth zould be fqlling out right noz:

I feel like such qn idiot right noz; cuw I cqnnot figure this si,ple thing:

I q, going OCD o, this qnd zill just go grqb q beer:

LOL; lqnguqge progrq, understood beer: ;)

I zill get this one zqy or qnother:

I cqnnot for the life of ,e seeing zhqt I doing zrong!:confused:
 

LynnM

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#10
The backfire sounded like a LOUD gun shot. Computer was a re man to vin # barely runs, hard to start before and after replacement... I originally thought the TC jumped it runs that bad...
 

nickb2

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#11
Well, finally figured out my keyboard problem.

Now I can actually read what I am writing. :D Yeah, loud gun shot sound, that is a big backfire.

At this point, anything is suspect. I will repeat myself again, how did you ascertain if the TC did not jump a tooth or two?

So as Kev2 said, back to basics.

I was smoking outside this morning, lady started her nissan. Piston slap for sure. I told myself in my head, that engine is not long for the road if she keeps driving it like that.

The only thing that can cause bad timing on these engines is a mechanical failure at this point as you state the PCM was vin# matched.

This thread is confusing me and my head hurts. If you put it on TDC, what is the timing saying?

Here is link to what I was trying to say before my keyboard went swedish.

http://www.justanswer.com/dodge/0ocyx-timing-spec-2000-dodge-dakota-3-9v6.html
 

nickb2

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#12
10 will give it some juice then the PCM should go back to 8 BTDC. You cannot manually set the timing on these engines at all.

Only way is to bypass the PCM. If you have crank and cam sense, your fine there.

I know the link I gave is for a 2000, but in essence, should be the same. Look for a cooked cam shaft. There may be a cam lobe that went south. My old 84 gt stang blew two cams on the eighth cylinder. Frustration and a lot of head scratching.

Anyway, again, good luck. Even with ford racing and MSD ignition, we could only come to the result that the exhaust lobe was burned again and backfired. Could not make a 13 on the strip.

If you have no end play on the crank, and TC is spot on, you are missing something here.

So that was my $.02
 
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#13
lets regroup - focus - truck runs barely BUT its running -
BASICS
What codes are present NOW -
What is fuel pressure AND pressure drop with KOEO ?
Is there spark at several plugs?
Use a noid light?
Engine vacuum?
engine compression?


The guessing I think TC = timing chain? if it jumped the PCM would likely generate a CMP CKP sync or correlation code. The reason I always ask about scanner.
The loud BANG - could have been exhaust backfire or intake back fire, only TESTING will get us answers.
A vacuum test will likely reveal any damage ie plenum, exhaust.
Did I miss explanation WHY you replaced PCM?
SWAG- 1st fueling issue, 2nd mechanical

if one of the asked for basic tests cannot be done we can suggest ideas to obtain that data.
 

LynnM

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#14
I thought timing chain too. Took the front cover off for inspection. Everything was Ok.. Originally had ign problems Changed coil & HT lead. Swapped ASD relay.. Still had problems could run for weeks and Some times I would start it and it would run for 30 seconds and quit. Would crank & crank NO start Fixed some water leaks while it was down... Weather has been lousy Will get back to it this week with a comp test and vacuum . I have a real cheap code scanner right now.. I thought I could use the cable from it, but It is powered differently.. Some POS broke into my Van and stole the connecting cable & a box of my tools 2th time that has happened in the last 5 years , last time they took the whole Van.. Recovered within 24 hours... Thanks LoJack
If I am still alive.. Some pos Teenager crashed into my Moms Buick today 2002 with 60K original miles Took two plugs out they were black....
 

LynnM

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#15
sorry it has been so long, I twisted my back up... Anyway I removed several spark plugs and attempted compression test NOT good pass side compression readings F/B 90/75/75 psi Dr side rear cyl 75 psi Looks like a valve job & rings Still undecided if I am just going to junk it...