Air Lock (1 Viewer)

[maximus]

Hello all,

I'm new here, and wouldn't you know it, I need help...

I bought a 1991 Hilux Surf 2.4 liter turbo diesel this summer (2L-TE). It ran great until the fall when it cooled down (approx. 4 deg. Celsius or so). Since then, it gave me problems starting at a such temperatures (or cooler) no matter what I did, including small shots of starting fluid / ether. I have replaced and tested the glow plugs-- they are brand new and definitely getting power... 12V for the first few seconds, then 6V thereafter, then after some time they shut off. From what I've read, this is normal.

Fast forward to now... I've managed to narrow the problem down to the fact that the fuel seems to be draining back into the tank over night. As a result, I need to bleed the system of air by loosening the banjo-bolt on top of the fuel pump, pumping fuel using the filter hand-pump (you can see little air bubbles coming out of the top of the fuel pump at the loosened bolt) and thereafter bleeding the system further by loosening the box nuts at the injectors and cranking the engine (i.e. to get the pump to force out any remaining air).

Even when there is absolutely no air in the fuel system the engine won't fire up. What I mean is, the starter motor will turn the engine over, but there will be absolutely no ignition of fuel no matter how long I glow (and re-glow the plugs). Even with shots of starting fluid, it seems to turn over a bit faster, but now ignition. The only thing I can do to get it started is to put it in a very well heated shop (approx. 24 deg. Celsius) for 8 hours and then it starts up immediately after having the air purged.

After going through the process above and finally getting it running (many, many times), it will fire up when cold with no problems for a day or two... then, again, it will have air in the system. On one occasion, the truck would not start when cold (i.e. -5 deg. or so) but when heated for 6-8 hours it did start immediately. I'm not sure whether there was air in the system that time or what the problem was.

To summarize, I have:

-replaced the glow plugs
-replaced all of the soft/rubber fuel lines
-installed a one-way non-return valve in the supply line as close to the tank as possible (in case the fuel was draining back through there)

I even was prepared to replace the hand-pump assembly on top of the fuel filter. I got a used one to replace and the guy I bought it from said the vehicle he removed it from ran for the last 3 months without a problem. When I got it home and tried to prime the system after installing it, fuel leaked out the top of the priming hand-pump... so if his could tolerate this kind of leak, why can't mine? In the end, I reinstalled my one priming hand-pump.

I've also left the cap off overnight to ensure that it is not "back pressure" in the fuel tank drawing fuel back into it.

So, after bleeding the system a few nights ago, the truck would not start this morning. Not even a little hint of firing up. The ignition would simply turn over and over.

I'm not sure if there is air in the line at this point (no time to investigate), but if the problem was that fuel was draining back to the tank through the fuel supply line then the one-way valve ought to have prevented this.

I **think** my question is this:

What is the problem???

Is it that the system is drawing in air overnight?? My theory was that it was doing this in the cold because some seal or hose fitting was shrinking due to the cold... given the difficulties when starting it in the cold after bleeding, could it be something else? Could it have another issue and could all of the cranking when cold be the cause of the air somehow??

I'm at the end of my rope right now and look forward to anyone's comments, if you've read through my long-winded plea thus far...

Thank you.

 

[2ndGenToyotaFan]

You have a 2L-TE..... I have no sympathy for you! (Also I know next to nothing about diesels....)

Lucky for you we have a member who knows his way around a 2L-TE... Dan! Get over here!!!!

Welcome to Mud <- You've been saluted!

 

[maximus]

Hi, 2ndGen- thanks for your reply.

I accept the salute! Good to be a member.

As for the "cheers"... well, I'm going to need a few more of those until I get it figured out. I'm pulling out my hair on this end and don't have too much to spare!

Anyway, if nothing else it feels good to vent to people who are willing to listen since my wife is tired of hearing all about "bleed back", "air locks" and "non-return valves"... thanks!

 

[2ndGenToyotaFan]

No problem Maximus, while we're waiting for Dan, do you have any pics of your ride?

 

[maximus]

Here it is... my ride, this summer when it was warm and my wife and I took it through the Kootenays...

 

[maximus]

Anyone?

 

[2ndGenToyotaFan]

Hey! I've been away... You Canukistanians have funny lookin' license plates....

Is that push bar thing stock? And you have the clinometer set too.... I'd be drooling, but I have the same one in my 4Runner! Great minds think alike!

I'll go find Dan and send him a message...

 

[maximus]

Hi 2ndGen,

Thanks for your help. I'm going to be playing around with the truck again today-- I'm thinking of bypassing the entire fuel filter assembly (for testing only) to see if that's the problem. Alternatively, I'm thinking of putting in a CAV type filter and a separate hand pump of some sort...

Thanks again.

 

[maximus]

2ndGen,

The "Sahara bar" is not stock, but I bought it like that, lights and all. The off-road lights are actually quite bright.

As for the altimeter/tilt-o-meter pod this actually is stock in Japan I think.

Anyway, I got the truck fired up today after bleeding all of the air out of it and heating it up in a warm shop with a high-wattage space heater blowing directly into the front grill. I then bypassed the fuel filter with a little piece of pipe because I suspect that it might be drawing in air through the fuel filter / priming hand pump assembly somehow.

If this fixes it, I'll be ordering a new priming pump assembly. Apparently, it's not uncommon for the diaphragm in there to wear out and leak air. I'm actually hoping that this is the problem, despite the CDN $120 I was quoted for a new one...

I'll keep you all posted.

Cheers,
Maximus

 

[DanS HJ-45]

And here I am (muchas gracias Jay-rod)...

There are two places you could be getting air into the system letting the fuel drain back down. Either the filter/primer pump is leaking, or you have a leak inside your fuel tank.

Does it still have this problem with a full tank of gas, or does it only act up when it gets low enough? My truck has a leak in the pickup line, and if I shut it down with less than 1/4 of a tank, it quickly drains back into the tank and the next start can easily require 15+ seconds of cranking to get the fuel drawn back up.

If it still does it when it's full, then it is pretty much narrowed down to the filter/primer. If the air leak were downstream of the filter, then it would simply drain back into the fuel filter and would still start fairly easily.

From the description you gave of the temperature causing this, I think that points more towards the primer leaking.

FWIW, the fuel will siphon/draw through capillary action back into the tank from the filter as well, which would explain why it's still takes a long time to start, even after bleeding the air from the system. If it cranks a long time, then starts smoothly, then that is exactly what is going on. Also, if it is the primer, then it is the same part as used on the North American 1L, 2L and 2L-T engines. I think I paid $25 about a year ago in Seattle for one at the dealer.

Dan

PS-I started my 2LT-E (with one battery) this morning at -17C without a problem, with the GPs kicking it does a fine job...

 

[2ndGenToyotaFan]

Thanks Dan! You the man

I got my clinometer set off of e-bay from New Zealand a while ago... It's sweet.... What's a "meter"? Hehehe

 

[maximus]

Dan and 2ndGen,

Thanks for the messages!

I did bypass the fuel filter assembly yesterday with just a short piece of pipe. We'll see if it gives me any problems today... If not, I'm going to try installing the used priming pump that I got from a guy up here who said it was working fine in the vehicle it's from 3 months ago or so.

I do suspect (read: hope) that the issue is the priming pump since it doesn't matter how much fuel is in the tank. Also, the tank seems to be "sealed" in that there is quite a bit of back-pressure when it's been running for a long time - basically, no air is getting in to replace the fuel that has been consumed. This would result in faster siphoning / bleedback of fuel into the tank, so I'm venting the cap after running the truck for a while. The cold weather would also cause whatever air there is in the tank to condense, resulting in additional back pressure. At least, that's my theory.

At any rate, it still had the same problem with the fuel tank cap off overnight, so fundamentally I still think it's the primer pump.

I'm happy to hear that if everything is OK the engine should start at around -20C. That's encouraging. I would like a block heater or in-line heater, but until this problem is cured there's not much point. Also, my wife and I are currently living in a condo which doesn't have power outlets at the parking spots. Maybe I need to go complain to the strata so that they do something about it as it does get pretty cold here (in the Okanagan).

Anyway, thank you all for the help. I'll keep you posted.

PS- 2ndGen: I think a meter in non-metric terms is something like four and one-half furlongs and eight cubits divided by six and three-quarters of a yard. But then, I operate in base ten as I'm Canadian!

 

[maximus]

Wouldn't start this morning... back to square one.

 

[2ndGenToyotaFan]

Wouldn't start this morning... back to square one.

Bummer.... Not even after mucho cranking? (That's spanish... )

PS- 2ndGen: I think a meter in non-metric terms is something like four and one-half furlongs and eight cubits divided by six and three-quarters of a yard. But then, I operate in base ten as I'm Canadian!

Bah! 10's are for shmucks!!! Give me a 12 anytime!!!! (Not really... I think the US is a little backwards in that aspect...)

 

[DanS HJ-45]

When you say it wouldn't start, do you mean that it wouldn't start at all, or that it still took lots and lots of cranking?

The tank having serious suction doesn't seem right. My tank has virtually no suction when I pull the gas cap off. Because I have a converted gas tank on mine, I have the fuel supply, the fuel return, and the original 3rd line--which I just left running up to the engine compartment and open to serve as a vent line.

When you pull the fuel line off of the filter to prime it, how hard is it to pull fuel up with your mouth (careful, but it's not that big of a deal--one more reason to switch to Bio!)?

If you pump the primer do you get fuel up into the filter? I installed a clear el-cheapo filter just prior to the expensive filter/primer to protect it, and also because it's real helpful to see the fuel and air (or lack of). When it's drained back in, it cranks and cranks until it fills ALL the way up, then catches instantly. Another thing you could try would be to remove the fuel inlet line from the filter/primer, and hold a cup of diesel in the inlet tube while pumping the primer. The fuel should get sucked up, and a loaded filter should be more than enough fuel to idle for 10 minutes.

Dan

 

[maximus]

DanS,

When it wouldn't start, it wouldn't start at all. No amount of cranking helped. All it did was drain the battery...

The fuel primer pump (hand pump on the filter) seems OK other than the fact that when I put compressed air to it it seemed to leak out. On the other hand, that's from a compressor to a low-pressure pump, so if the diaphragm flexed a bit and let out air, it wouldn't be much of a surprise.

The funny thing was, tonight, after "super"-heating it with a space-heater aimed right at the front grill, it started with not too much fuss (a few seconds of cranking), despite the air that I think may have been in the injector pump.

Anyway, I was ready to take the fuel pump apart and rip everything out. Then, I had a thought about the banjo bolt... I originally thought it was in the pump to expel some of the extra fuel into the return line, both from the injector pump and from the engine. After taking the banjo fitting apart, I figured out that the purpose of the banjo bolt on the fuel pump is only to expel air from the injector pump... long story short, there is a small sieve at the bottom of the banjo bolt and a tiny little hole at the top that links to the return line. This seemed to be plugged with crud (wouldn't even let compressed air through). I cleared it out by blowing compressed air through it backwards... Also, it seemed to be missing a crush washer / gasket on top of the banjo bolt which I likely lost while taking it apart some time ago. So much for the "long story short thing"...

So, my theory right now (and I'm hoping it's accurate) is that the injector pump was completely unable to expel any air through the banjo bolt and that this is the entire purpose of the banjo bolt. So, an air-pocket would develop at the top of the pump during use. Then, when cold, the pump would try to force fuel through to the injectors but it would only push air and a small amount of fuel through. Also, it would compress the air that was stuck in the pump, causing some back-pressure which would force fuel back into the tank when the truck was not running.

The big question is why would it start when warm but not cold? My theory (part 2) is that it was able to force the air through the injectors and "burn it off" causing a lot of smoke when the ambient temperature was decent. But, when cold, the engine just couldn't deal with a mixture of both fuel and air drizzled through to the injectors in the cold temperature and this would end up flooding it.

Well, that's my theory, at least. I'll hope tomorrow proves me right. But everything I've heard indicates that when there is air in the engine, most people can just crank the engine (and thus the injector pump) over and over until it starts, which I was never able to do. In my case, it simply wouldn't start.

This makes sense, because on a properly functioning fuel system, the injector pump ought to force any air out through the banjo bolt until the pump builds up enough pressure to properly inject fuel into the engine- and then the engine ought to start. Also, while running, the system ought to be able to expel any air back into the fuel tank via the banjo bolt and then the return line.

So, my theory- the banjo bolt sieve was plugged with crud. Or so I hope.

As always, I'll keep you all posted with respect to my trials and tribulations.

Thanks again for your thoughts!

 

[maximus]

Update: the truck started immediately this morning. However, it was approximately +3C this morning. As well, the engine was likely still somewhat warm from last night, so that may all have played a role. I guess time will tell.

 

[maximus]

Just got a call from my dad, who is truck-sitting for me. He let the engine cool down completely (it's approx. 0deg C right now) and suddenly it wouldn't start at all. As always, it cranks over, but doesn't fire up.









I don't know what else I can do at this point.

 

[2ndGenToyotaFan]

That's so odd.... You'd think that the temp dropping would make it harder and harder to start... not just stop it all at once...

Have you tried all this with the fuel tank cap off? You were saying that your tank seemed to be sealed up really well.... and Dan said he has an extra (Or something like that) vent.... Maybe your tank is so sealed up, that the fuel can not overcome the suction? When the temo is up, al the diesel and air in the tank would expand, causing less vacuum, or maybe a pressure in the tank.... Just thinking out loud...

 

[maximus]

2ndGen,

Keep thinking out loud, I appreciate it.

Yes, this was all with the tank cap off-- it's been off all night, too.

Great minds really do think alike!