1981 I-mark (4FB1) cold engine rough starting

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Mon Sep 25, 2017 7:43 pm

so, i'm not finding and points of high resistance between the alternator and battery positive terminal. in fact, the entire path from the charging terminal on the back of the alt all the way to the battery only has 2.5 ohms of resistance.

is it possible that my charge relay is creating the drop in potential?

i always assumed that the charge terminal on the alternator had a direct high-gauge cable path to the battery positive terminal, but the charge relay seems to be in that path and that is something i haven't encountered before.

thanks!

casey
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Sat Oct 07, 2017 3:41 pm

Well, my voltage regulator completely went out over the last couple of days; which caused the voltage of my charging system to start varying between 10 volts (at idle, under load) to a little over 16 volts (at high RPMS with the headlights off). Obviously, this pressed the issue of changing my alternator and I got it swapped out the day before yesterday with a spare alternator that I rebuilt a couple of years ago. Now that the alternator is properly charging the battery, the engine is starting MUCH better... thanks for the suggestion gearbox, it seems that my glow plugs were not heating up properly.

However, the engine still definitely starts a bit rough, and idles really shakily for the first few minutes the engine is running, so I would like to brainstorm what might be causing that... my next idea is to do a valve adjustment and run some diesel purge through the IP/lines/injectors to clean them out a bit.

Does anybody have any other suggestions for what might be causing the rough running engine in the mornings? I also notice that the engine is a bit shakier than normal even after it is fully warmed up... but it isn't anywhere near as pronounced as when it first starts up.

Thanks!

Casey
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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Halden
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby Halden » Mon Oct 09, 2017 12:12 pm

I know it sounds stupid.... But what is your idle set at?
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Mon Oct 09, 2017 12:47 pm

if my tachometer can be believed, my idle speed is set stock... about 750-800 RPMs.

i suppose i could try raising it, but the idle speed hasn't changed at all in the time i've owned the car, and the shaky stumbling cold starts is a new issue.

thanks!

casey
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby puttputtinpup » Mon Oct 09, 2017 1:47 pm

Change the little vacuum hoses from the back of the alternator, to the fast idle activating solenoid, then from there to the fast idle diaphragm at the back of the injector pump. If you have AC, there may be a T and another hose running through the firewall. Maybe you could trim the end and put it back onto the T. But 1st, pull the hose off the fast idle diaphragm, put a new piece in its place, draw a vacuum on the other end like using a straw in a milkshake. See if the diaphragm leaks down. If it does, that could be your problem. Somebody here used a replacement off a Mazda and worked quite well. Anyway, rule that out.

IMy 1st pup had the same rough idling issue way back in 91. The diaphragm had a hole in it. Tried to fix it, but didn't last long. I just adjusted the idle stop bolt on the injector pump a little. Helped a lot
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby puttputtinpup » Mon Oct 09, 2017 1:55 pm

pitch4pd wrote:For the fast idle diaphram, I just replaced mine with "Fuel Pressure Regulator, Mazda S210 61 601A , s21061601a KP253" as suggested somewhere on this forum (I can't find the thread). It is not a direct fit but a hose clamp and a crimp connector was good enough to make it work. The fuel pressure regulator has a screw to adjust the stroke length so it is easy to make work without taking exact measurements. I also ran a separate switch for the solenoid so I decide when it fast idles.

I'll keep looking for the original post about the Mazda part.
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby puttputtinpup » Mon Oct 09, 2017 1:59 pm

A bit more information and pictures here: viewtopic.php?f=1&t=19240&p=124074#p124074
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby Halden » Tue Oct 10, 2017 7:34 am

cocheeze wrote:if my tachometer can be believed, my idle speed is set stock... about 750-800 RPMs.

i suppose i could try raising it, but the idle speed hasn't changed at all in the time i've owned the car, and the shaky stumbling cold starts is a new issue.

thanks!

casey



Just thought Id ask on the off chance it was low.
It's not pronounced "Ih-soo-zoo", it's pronounced "It-screws-you"

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Wed Oct 11, 2017 11:43 pm

puttputtinpup wrote:Change the little vacuum hoses from the back of the alternator, to the fast idle activating solenoid, then from there to the fast idle diaphragm at the back of the injector pump.

I haven't changed the hoses entirely, but I did cut off the loose half inch or so from the ends of the hoses at all of the connection points and re-attach the hose so it fits tightly. I did that at all of the points you mentioned above.

puttputtinpup wrote:If you have AC, there may be a T and another hose running through the firewall. Maybe you could trim the end and put it back onto the T.

I do have AC, but there isn't a T or another hose leading to the firewall. Not sure why?

puttputtinpup wrote:But 1st, pull the hose off the fast idle diaphragm, put a new piece in its place, draw a vacuum on the other end like using a straw in a milkshake. See if the diaphragm leaks down. If it does, that could be your problem.

Will do. I meant to ask... about how much should the diaphragm move the cable when it is working correctly?

puttputtinpup wrote:Somebody here used a replacement off a Mazda and worked quite well.

I actually bought one of those a while back, so I have it on hand if it is needed.

Thanks for the suggestions!

Casey
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby greg_a_morton » Sun Oct 15, 2017 7:50 pm

What are the sizes of fuel lines they look like different sizes to me!

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Mon Oct 16, 2017 7:45 pm

greg_a_morton wrote:What are the sizes of fuel lines they look like different sizes to me!


not sure which fuel lines you are referring to, greg?
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

greg_a_morton
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby greg_a_morton » Fri Oct 20, 2017 7:57 am

ip lines to filter and return lines they look like several different sizes in that small area

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cocheeze
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Mon Oct 23, 2017 11:02 am

greg,

sorry, i am still not sure what picture you are referring to. i haven't posted any photos of my engine compartment in this thread... so i don't know exactly what picture you are referencing.

all of my hose sizes are stock, unless i am mistaken.
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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cocheeze
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Posts: 366
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Location: Portland, Oregon

Re: 1981 I-mark (4FB1) cold engine rough starting

Postby cocheeze » Mon Oct 23, 2017 11:13 am

well, i have made a bit of progress with my cold staring issues. it still isn't great, but it is much improved.

the latest thing i did was apply vacuum to the fast idle actuator per puttputtinpup's suggestion... i noticed that it wasn't leaking down, but it also wasn't contacting the throttle assembly at all so it wasn't increasing the idle during cold starts.

i was able to get it adjusted so that the actuator opens the throttle a bit, and it has started much better since.

i still think a valve adjustment and some other preventative maintenance items are in order, but for the time being it seems like the hard start problem has been solved.

looks like it was a combination of:

- poorly charging alternator causing weak glow plugs
- bad fusible link connection causing intermittent glow plugs
- vacuum lines old and cracking at connections, probably leaking vacuum
- fast idle actuator not making contact with the throttle linkage when fully actuated

as always, thanks for all the help/suggestions!

casey
'81 Isuzu I-Mark Diesel (100% wvo) 220k
'81 Isuzu I-Mark LS Diesel 219k
'81 Isuzu I-Mark Coupe Diesel 143k
'81 Isuzu P'up Diesel 4wd (100% wvo) 310k

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puttputtinpup
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Re: 1981 I-mark (4FB1) cold engine rough starting

Postby puttputtinpup » Mon Oct 23, 2017 12:23 pm

Sounds good, Casey...Glad it's doing better now.
Last edited by puttputtinpup on Wed Oct 25, 2017 12:58 am, edited 1 time in total.
Reason: As promised. Edited
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