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Author Topic: 87 2.5 timing  (Read 1940 times)

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dudley

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87 2.5 timing
« on: January 04, 2011, 09:35:59 AM »
Rebuilt my engine.  87 Renix 2.5 in a comanche.  Is it possible to have the distributor one tooth off and the computer will compensate enough that at an idle it will be at 10 degrees BTDC, and at 3000 rpm not under a load be at 22 to 25, but under a load like going uphill at higher rpms can't compensate enough so I loose power?
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Offline dwtaylorpdx

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Re: 87 2.5 timing
« Reply #1 on: January 04, 2011, 09:50:46 AM »
You said rebuild, so I gotta ask, are you positive you got your cam timing correct?
And did you check the cam timing with a dial indicator not just rely on the timing marks?
Assuming you got a new cam there should have been a timing curve chart in the box,
that you use with a dial indicator on the pushrod end of the rocker. Its easy to do with
the engine in the car just have to take the valve cover off.

There are a lot of easier things that could cause the problem...

I thought my engine had issues when I rebuilt it turned out the TPS went sour the day I pulled the engine...
Drove me crazy for a week after I put the motor back in.

Start with all the basics ignition, fuel, vacuum leaks etc.

Dave
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dudley

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Re: 87 2.5 timing
« Reply #2 on: January 04, 2011, 11:11:09 AM »
had the engine rebuilt by a reputable rebuilder.  ASSuming they did everything correct. No new cam. It only had 60,000 on it.  No vacuum leaks. I did rebuild the Throttle body. I am sure everything went in the way it came out.
The other problem I have is it will not start cold. It starts and immediately dies. I have to feather it to keep it going for about 30 seconds then it idles.  Took the gas line loose from the TB and gas squirts everywhere, so pressure is good.  New Idle Motor so it works.
I asked a mechanic and he said maybe one tooth too far advanced might be causing it all.
PERPLEXED I am!!!!!
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Offline sharpxmen

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Re: 87 2.5 timing
« Reply #3 on: January 04, 2011, 11:20:08 AM »
how do you know the pressure is good? (i'm not saying it isn't but the fact that fuel comes out thru the hose doesn't mean you have the correct pressure).

sounds like you're short on gas though if it fails at cold, i would also check the MAP sensor, the PCM temp sensor and the O2 sensor. Any codes? (I assume TBI also has CEL light but not sure).

If you think the distributor is off by a tooth then you should start there - verify that is timed correctly, don't know what the timing should be on the TBI but 10 deg doesn't sound that would be off by 1 tooth though (can you adjust the timing on the TBI by rotating the distributor or is it controlled by the PCM as with the newer models?)
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Offline chardrc

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Re: 87 2.5 timing
« Reply #4 on: January 04, 2011, 01:00:14 PM »
Quote from: sharpxmen on January 04, 2011, 11:20:08 AM
(I assume TBI also has CEL light but not sure).
 (can you adjust the timing on the TBI by rotating the distributor or is it controlled by the PCM as with the newer models?)
tbi doesn't store codes and controls the timing so can't adjust by rotating. the distributor shaft end is a slot so your either on or 180* off. 

may want to check fuel pressure with a gauge because depending on how rigorous of a throttle body rebuild you did that would include the fpr so the pressure could be off from that.
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Offline sharpxmen

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Re: 87 2.5 timing
« Reply #5 on: January 04, 2011, 01:08:33 PM »
Quote from: chardrc on January 04, 2011, 01:00:14 PM
the distributor shaft end is a slot so your either on or 180* off. 

that's the oil pump drive and you can move it around to line up with the dist shaft so 1 tooth can be off, but it just doesn't sound like 10 deg is that much off.

Don't know what the TBI timing is like (value at idle) but since he can adjust it maybe find the value and set it properly. Also, is there a vac advance? if so does it have 2 hoses or just 1 (thinking if maybe he got them swapped, if it's just 1 line then disregard).
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dudley

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Re: 87 2.5 timing
« Reply #6 on: January 04, 2011, 08:29:08 PM »
Distributor doesn't move and no vac advance. Put my finger over #1 cylinder and got it to top and with barely moving the H balancer had it at 10 degrees. Worked at oil pump until when getting distributor in the rotor was directly centered on #1 cap terminal.  Think that should be correct, right?
I will check fuel pressure.
New MAP sensor, but I will check it, and and only parts replaced on TB rebuild was o-rings, seals, and the small filter on the injector.  Didn't touch other things, not eve the TPS.
Don't know if it has a check engine light. Never come on if it does.
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Offline sharpxmen

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Re: 87 2.5 timing
« Reply #7 on: January 04, 2011, 09:12:22 PM »
Quote from: dudley on January 04, 2011, 08:29:08 PM
Distributor doesn't move and no vac advance. Put my finger over #1 cylinder and got it to top and with barely moving the H balancer had it at 10 degrees. Worked at oil pump until when getting distributor in the rotor was directly centered on #1 cap terminal.  Think that should be correct, right?
I will check fuel pressure.
New MAP sensor, but I will check it, and and only parts replaced on TB rebuild was o-rings, seals, and the small filter on the injector.  Didn't touch other things, not eve the TPS.
Don't know if it has a check engine light. Never come on if it does.

you need a timing light

with points you can set the timing static like you describe but i never seen or done it this way on an electronic ignition, with points you set the advance and then you rotate the distributor until the points disengage (with a check light) but even then you need to double check with a timing strobe light to make sure.
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Offline chardrc

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Re: 87 2.5 timing
« Reply #8 on: January 04, 2011, 09:36:44 PM »
1988 jeep Fsm

" Distributor
all models are equipped with a renix solid state ignition module. renix system uses a TDC sensor mounted near the flywheel. the distributor consists of a cap and rotor. its only function is to distribute high voltage to appropriate spark plug. no adjustments are required on either system.

Ignition timing
Note: No adjustment is possible on models with renix ignition."
« Last Edit: January 04, 2011, 09:38:53 PM by chardrc »
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2007 jk Rubicon 2dr

Offline Jeffy

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Re: 87 2.5 timing
« Reply #9 on: January 04, 2011, 09:53:54 PM »
Hey chardrc, if you want to collect all of the images for me and put something together, I'll post it to the FAQ.
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Offline sharpxmen

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Re: 87 2.5 timing
« Reply #10 on: January 04, 2011, 10:47:31 PM »
Quote from: chardrc on January 04, 2011, 09:36:44 PM
1988 jeep Fsm

" Distributor
all models are equipped with a renix solid state ignition module. renix system uses a TDC sensor mounted near the flywheel. the distributor consists of a cap and rotor. its only function is to distribute high voltage to appropriate spark plug. no adjustments are required on either system.

Ignition timing
Note: No adjustment is possible on models with renix ignition."


nevermind then, i thought it can be adjusted (i misread your prev post) - then it's not the timing for sure, sounds like he positioned it right by what he described.
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Castr8r

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Re: 87 2.5 timing
« Reply #11 on: January 04, 2011, 11:36:03 PM »
The distributer can be installed one tooth off; I know 'cause I did it!  In my case, it ran; just didn't run well.  I'd pull the dist. and re-install it following the procedures in Haynes/Chiltons. 
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Offline chardrc

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Re: 87 2.5 timing
« Reply #12 on: January 05, 2011, 08:38:05 AM »
Quote from: Castr8r on January 04, 2011, 11:36:03 PM
The distributer can be installed one tooth off; I know 'cause I did it!  In my case, it ran; just didn't run well.  I'd pull the dist. and re-install it following the procedures in Haynes/Chiltons. 
your right.. i was wrong in my first post  :flush:.... wasn't feeling great yesterday (but my quote from the fsm is right).. anyways incase you don't have the Haynes manual here is the abbreviated procedure.

"a. make sure #1 cyl is at TDC
b. Put a screwdriver into the the oil pump gear slot and rotate it so the gear slot is slightly past the three o'clock position.
c. install the distributor with the rotor to the five o/clock position
d. with the distributor fully engaged in its correct location, the rotor should be pointing to the six o'clock position. "

Jeffy where you talking about all the fsm pdfs? i think i have all the section relating to the 2.5l tbi but may be missing a few (just downloaded form a website i had found.) I'll have to figure out how to combine the pdfs if you want 1 file... or I could just give a link to the site if you just want to add a link to the list like the other fsms where.
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1990 YJ 4cly, ax5, 2.5 inch BDS lift, 31 MTr\'s,  Powertrax-lockers all around, track-bars removed, boomerang shackles, warn m8000 winch, electric fan. [sold but not forgotten]

2007 jk Rubicon 2dr

dudley

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Re: 87 2.5 timing
« Reply #13 on: January 05, 2011, 08:44:24 AM »
Quote from: chardrc on January 05, 2011, 08:38:05 AM
your right.. i was wrong in my first post  :flush:.... wasn't feeling great yesterday (but my quote from the fsm is right).. anyways incase you don't have the Haynes manual here is the abbreviated procedure.

"a. make sure #1 cyl is at TDC
b. Put a screwdriver into the the oil pump gear slot and rotate it so the gear slot is slightly past the three o'clock position.
c. install the distributor with the rotor to the five o/clock position
d. with the distributor fully engaged in its correct location, the rotor should be pointing to the six o'clock position. "

Jeffy where you talking about all the fsm pdfs? i think i have all the section relating to the 2.5l tbi but may be missing a few (just downloaded form a website i had found.) I'll have to figure out how to combine the pdfs if you want 1 file... or I could just give a link to the site if you just want to add a link to the list like the other fsms where.

Thanks for this. My Chilton is no where near this detailed!  I will double check it tonight!
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