4.2 MPFI conversion help - Off-Road Forums & Discussion Groups
Go Back   Off-Road Forums & Discussion Groups > Jeep > Jeep-Short Wheelbase

Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK



Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 09-25-2003, 10:28 AM
LAFEET
Guest
 
Posts: n/a
Default 4.2 MPFI conversion help

4.2 MPFI conversion help
hey there

i'm doing a conversion on a 87 yj using 94yj mpfi parts, i
got it all wired up, and i know the mechanical timing is right.

but it will not run , it tries but all it does is pops and sputters, it does not matter how i turn the dist, (i broke the tab thats how i can turn it). i changed the coil, tps, iac, i had extras there not new. it has new rotor, cap, wires, plugs, still the same.

i pulled off the fuel rail to watch the injectors fire, they seem to work fine, BUT shouldnt they shoot just one time per rev.????? there shooting 2 - 3 - 4 times per rev., and i dont thinks thats right.

i'm new to the fuel injection world, and i dont have a way to check for fault codes, i dont know what to do.
can you give me any ideas!!!
thx
jerry
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
Sponsored Links
Advertisement
 
  #2  
Old 09-25-2003, 03:15 PM
jeeperjohn's Avatar
Can't Get Enough
 
Join Date: Sep 1999
Location: The Plywood State.... Florida
Posts: 1,340
Thanks: 0
Thanked 0 Times in 0 Posts
jeeperjohn is on a distinguished road
Default Re: 4.2 MPFI conversion help

Not sure about any codes. I am in the process of collecting parts for fuel injection using the 258 head with a high output 4.0 intake and throttlebody with a MegaSquirt controller. So I have no experience with the Jeep FI system. This came to mind (you did not mention any work being done to the intake).
If you are using parts off a 94 (not the MPI kit) and a 258 head, did you redrill the intake for the dowel pins on the head that locate the intake? If not it should have a massive vacuum leak. If you are not using a 258 head are you using a High output 4.0 head or a standard 4.0 head. Yes, they are different.
The upper hole is the one that has to be drilled. Aparently, the lower part of the intake flange will have to be trimmed also

Also see http://monsterslayer.com/jeep/40Head/40Head.htm
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #3  
Old 09-25-2003, 06:59 PM
LAFEET
Guest
 
Posts: n/a
Default Re: 4.2 MPFI conversion help

hey everyone
i'm posting this on a bunch of different boards, hopefully sombody can help

this is a 4.2 mpfi & 4.0 HO head conversion on a rebuilt motor

using 4.0 factory wiring
its in proper time (NOT 180 out)
the firing order is correct
all the valves open and close in relation to the dist.
using factory in tank pump
factory CPS
94 4.0 HO flywheel (so i was told)

everything i have tried to do so far makes no difference in the way it TRIES to run

today i figured i would change the plugs thinking they might be oil fouled. i found out they were not even the right plugs, they gave me the wrong ones to start with, i didnt know i had nothing to compare them to.
put the new ones, thinking this would fix it (NOT) it tries to run exactly the same.

i pulled the codes up
here they are

12 Battery or computer recently disconnected
33 Air conditioning clutch relay circuit open or shorted
(may be in the wide-open-throttle cutoff circuit)
41* Alternator field control circuit open or shorted
54 cam sensor inside the dist.

the only real problem hear is #54
so i got another from a parts store, put it in
TRIES to run exactly the same, no change, and all the codes listed above are still coming up, includind 54

i hav'nt actually check the fuel pressure at the fuel rail (no guage) but i had the fuel rail off and watch the injectors shoot, and the seemed fine, even fired in the proper order 1 5 3 6 2 4, i did notice that they fired more than once per rev.
i dont know if that is right or not.

and its firing on all the cyls i can tell the header gets hot at each exhaust port.

but it will not run, i'm stuck thats why i'm posting this everywhere hoping sombody can help.

thanks much
jerry
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #4  
Old 09-25-2003, 11:08 PM
Old Hand
 
Join Date: Sep 1999
Location: San Diego, CA
Posts: 900
Thanks: 0
Thanked 0 Times in 0 Posts
raymo is an unknown quantity at this point
Default Re: 4.2 MPFI conversion help

That sounds like the crank position sensor isn't quite lined up correctly, or is too close or too far from the flywheel or damper (depending on how you are doing it). Have you played with it yet?
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #5  
Old 09-25-2003, 11:27 PM
LAFEET
Guest
 
Posts: n/a
Default Re: 4.2 MPFI conversion help

i pulled the cps out to look at it then put it back in, want to see if it was hitting.

theres not realy no adjustment it fits on two necked bolts.
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
  #6  
Old 10-02-2003, 07:36 PM
LAFEET
Guest
 
Posts: n/a
Default Re: 4.2 MPFI conversion help

hey everybody

just wanted to let you know it started right up with the RIGHT FLYWHEEL, seems to run perfect, still have a lot more to do before its on the road though.

i know now how to wire up a mpfi with a factory harness, its not hard & its a hell of a lot cheaper than buying a aftermarket harness.

thank you again for all your help.

if i can return the favor let me know.
thx again
jerry
Digg this Post!Add Post to del.icio.usBookmark Post in TechnoratiFurl this Post!
Reply With Quote
Sponsored Links
Advertisement
 
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -5. The time now is 01:12 PM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.2.0
Copyright 1994-2009, VerticalScope Inc. // Off Road forums & discussion groups sitemap
side by side | atv | dirtbike | snowmobile | sandsport | competition | land use | Jeep | Toyota | Ford | GM