Issue starting when engine is hot (1 Viewer)

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Joined
Oct 4, 2020
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Location
Costa Rica
Hello,

Have been brainstorming for a while on that one without cracking that nut, so looking for some help/guidance.

Driving a PZJ70 from 1993 in Costa Rica, where it is >25C most days....

It used to be that we would wait for the glow light to go off on every morning before starting the engine and then never bother for the rest of the day. About a year ago, it started to have some more trouble to start after the first morning start.

For example going on highway for like 1h, stopping to fill up the tank and we would need to glow again for the whole glow timer, otherwise it won't start. When trying to start too early, it would act as if the battery is almost dead, very slow/painfull rotation by the starter. Going for another full glow timer duration, and it would start easy peasy, like the battery is back to life! Obviously the engine was still hot, and the battery is the same...so why?

Have been looking here and in some other forum and did some test today with my voltmeter.
When the key is on the glow position, i measure 10.2v on the glow rail for like 6s. Expected.
After the glow light goes off, i still read 10.2V. is that normal? I was expecting lower or even 0.
While we go to start, then it fluctuates between 8 and 6V until the engine goes and then it is 0v.

I am puzzled and would like to understand why the glow keeps on going after the timer(6s) and if it is normal. I was suspecting at some point that the glow was taxing the battery and preventing the proper start, but it seems that it keeps on going anyway, so not sure where to look now.

Any ideas of what to test? What to look for?

Geraud.
 
do a load test on your battery. as to the glow cycle yes my understanding is that it would do a full V glow for a short time then switch to like half V from the first. do you have a engine manual? they would have a few tests to do to check the condition of the different glow parts. I would not think that you would need much glow, especially once warm. maybe the coolant sensor is bad that the glow system relies on?
 
do a load test on your battery. as to the glow cycle yes my understanding is that it would do a full V glow for a short time then switch to like half V from the first. do you have a engine manual? they would have a few tests to do to check the condition of the different glow parts. I would not think that you would need much glow, especially once warm. maybe the coolant sensor is bad that the glow system relies on?
Yes, i have the engine manual, and did all the continuity test on each glow plug. Everything looking good. There is no test/verification for the timing of glow, hence my questions 😉

When you asked about the coolant sensor, are you refering to the water temperature sensor? There is one test i could not do for the water sensor as it is very tricky to reach and could not use my voltmeter on that crowded space. Looks like i need to dig deeper on that guy i guess...

Thank for the pointer!
 
there usually is a separate water temperature bulb for the glow plug system, just don't know about the PZ/HZ. there should be tests for the glow system timer and such, more than just the glow plugs.
the puzzling thing for me is that the glow system still comes on when the engine is hot and you are in a warm country. this tells me there is something wrong with either the temp sensor for the glow system or with the timer. i don't know anything about the PZ/HZ and don't have any engine manuals for these engines.
 
.When trying to start too early, it would act as if the battery is almost dead, very slow/painfull rotation by the starter.
The glow plug issue is a red herring. That is just a coincidence.

A good starter and battery will rotate an ice cold (or hot) engine no problem. Glow plugs irrelevant. It won't necessarily start, but it will rotate fine.

I would check the following:
- battery terminals. Are they tight? Do they move at all when you try to turn them by hand?

- battery corrosion. Remove the terminals and clean the inside ring completely. And battery posts.

- clean up all ground wires, including the wiring going to the starter. Clean the contact points until they are shiny underneath.

- if none of that works, get the battery tested.

- if the battery is fine, your starter is likely sticking when it's hot.
 
The glow plug issue is a red herring. That is just a coincidence.

A good starter and battery will rotate an ice cold (or hot) engine no problem. Glow plugs irrelevant. It won't necessarily start, but it will rotate fine.

I would check the following:
- battery terminals. Are they tight? Do they move at all when you try to turn them by hand?

- battery corrosion. Remove the terminals and clean the inside ring completely. And battery posts.

- clean up all ground wires, including the wiring going to the starter. Clean the contact points until they are shiny underneath.

- if none of that works, get the battery tested.

- if the battery is fine, your starter is likely sticking when it's hot.
Thanks for all the susggestions.... I did the battery checks and it was all good, did more cleanup of not so dirty battery terminals, ensure they were properly seated on the battery, it kinda help, but not for long....Well at least I passed the technical control in between, with no issues.

While looking for the battery cable, there was 2 from the (-) terminal, one not too big that goes straight to the chassis and another much bigger, going to the engine. The one to the engine is cleary dammaged and rusty just few cm from the engine, so I will assume it is the root of my problem. Once I can source a cable big enough, I will replace and update here.

As I was tracking those cable down the engine bay, a pipe close by got my attention. It goes from the vacuum pump (front of engine) to the back of the engine (touching the batery cable at the rusty point, hence my curiosity) but is not connected to anything on the other side. So I am wondering if it is expected. Here it is, in red, from RM183E (BR-49):
1680485952702.png

Any help in confirming where it should connect to on the other end? I could not figure that out from the documentation....
Or is it just connecting to nowhere, but then why is it going so far :)?

Thank you!
 
there usually is a separate water temperature bulb for the glow plug system, just don't know about the PZ/HZ. there should be tests for the glow system timer and such, more than just the glow plugs.
the puzzling thing for me is that the glow system still comes on when the engine is hot and you are in a warm country. this tells me there is something wrong with either the temp sensor for the glow system or with the timer. i don't know anything about the PZ/HZ and don't have any engine manuals for these engines.
Based on all your suggestions/observations, I kept on digging in the documentation and finally understood that Toyota had 2 systems:
-Super Glow Type which matches your description with sensors and different voltages based on time/temperature
-Fixed Delay Type which is much more simple (no sensor, always full voltage, fixed timing....) and is the one in my truck
So, I was not looking at the right spot....Anyway, looks like I might have found the issue, see my other reply in that thread.

Thank you!
 
Best thing is to allow the glow plugs to perform their initial cycle. Glow plugs use lots of power and hence your starting sucks. We run tons of Toyota's and everyone of them will suck at starting if you don't allow the glow cycle to finish.
I can hear the difference anytime someone tries to start without first allowing the glow cycle light to go out.
 
Make certain your primer is stiff before starting. If primer takes more than a few pumps before stiff then suspect a vacuum leak...sucking air.
 

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