Losing prime overnight (or sooner) 1HZ (1 Viewer)

[roscoFJ73]

Engine/IP have about 300,000Km's so the IP is probably getting old anyway. I have a used one coming in the mail that I was planning to send back out for a rebuild to have it on hand.

These pumps usually wear out and lose pressure at high speed. Its because the plunger and pump have lost their tolerances . But they still work ok at low rpms. Bearing noise and clatter from the timer piston are other symptoms of a bad rotary pump.
My gut feeling is its something to do with fuel delivery. A lot of 7* and 6* series get rust around the fuel pick up and this affects fuel flow. This tends to happen when driven on salted roads

This really why you need to do the 2 tests I outlined. Once you send them to a fuel injection shop, they can tell you anything.

 

[SKULLYOTA]

I don’t know if this is contributing to my problems, but I noticed this wetness at the back of the head…..head gasket weep? How worried should I be? It’s definitely coming from between the head and the block and not leaking down from the valve cover

 

[roscoFJ73]

I think its unlikely the source of your problem but sometimes bad head gaskets allow small amounts of coolant into the combustion chamber.
I would check the coolant level and oil condition.

 

[mudgudgeon]

It also seems to crank for awhile before starting and just doesn’t want to idle unless I run it out with the pedal for awhile. Also doesn’t seem to matter if it’s been sitting for 5minutes or five days. I can still pump the primer about ten times before starting either way.

You're getting air into fuel lines somewhere.

A cracked hose, or cracked hard line somewhere.

Run a piece of clear hose from filter to IP and poke it out the side of the hood so you can watch for bubbles.



This is on a vehicle that started fine, idled fine, and mostly ran fine. It coughed and stumbled on hard acceleration, and blew white smoke out the back.

 

[mudgudgeon]

I don’t know if this is contributing to my problems, but I noticed this wetness at the back of the head…..head gasket weep? How worried should I be? It’s definitely coming from between the head and the block and not leaking down from the valve coverView attachment 2726022

I would not be losing any sleep over this

 

[RandyMarsh88]

I recently had trouble with my 80 losing prime while driving. Replaced the filter cap, thought it was all good but the problem came back pretty quickly. Turned out to be related to the Sub tank being empty, the solenoid valve must not seal properly.

I'd had it for a year and had used but never emptied the Sub tank.

Narrowed it down by using clear PVC tubing in place of the fuel line. First from the filter cap back to the last section of hard piping (@ the firewall) then from the filter cap to the main tank. Bingo, no air bubbles.

Drove it back home and while underneath looking at the sub tank, realised it was empty and that's where the 'air leak' could be. Put 20 litres in and connected the fuel lines back as normal except for the last section to the filter cap, so I could watch for bubbles.

Selected the Sub tank and fired her up. Watched the bubbles gradually disappear and went for a drive, gave it a good workout. Symptoms gone.

Haven't fixed the cause as yet but I know to avoid running the Sub tank out for now.

Do you know what size tubing to use for this? I think I'm going to have to do the same thing.

 

[sunrk]

On a factory 1hz 80 the fuel lines are 8 mm. On a factory turbo 1hdt 80, they're usually 10 mm. Remember also that there is no 'pump' in the tank - it's all vacuum draw.

I went through this sort of stuff with clear hose trying to nut out the rough idle, funny start-up, etc. with my 80's 1hz and never got the answer. The idle speed still varies between 650 and 800 on startup and I'm unable to figure out why. It also seems to change depending if the motor is hot or cold (again no clear pattern to it). I've fiddled with the idle setting bolt on the injector pump but not touched any of the other adjustments.

I didn't find air in the fuel lines, but decided to replace the fuel hoses either side of the filter/primer head anyway with nice gates 8 mm fuel hose. Any time is a good time to fit a new genuine fuel filter btw noting that there are two types that fit (one is shorter than the other).

A bunch of yrs ago I pulled and replaced the main fuel tank pickup and level sender unit, and found a few things. The tank had a lot of junk in the bottom (not surprising after 25 ish years), and one of the baffle plates had partly come loose. I'd have to replace the tank with a new one to correct that. Now my 80 has no spare under the back and it's mounted on the rear bar/carrier I could fit a long range tank but can't justify it.

 

[roscoFJ73]

Do you know what size tubing to use for this? I think I'm going to have to do the same thing.

My video. I think you need an 8mm ID hose. My leak was around the fuel filter. It would run if I pumped it now and again.

 

[mudgudgeon]

My video. I think you need an 8mm ID hose. My leak was around the fuel filter. It would run if I pumped it now and again.

That's a lot of bubbles?

 

[roscoFJ73]

That's a lot of bubbles?

Sure was. The engine would peter out and I had to pump it. I dont know what I did wrong that day. I had the filter on and off 3-4 times.

 

[lowtideride]

Running into the same problem. About 2 weeks ago I had the window down and heard the "buzz" of a belly of air in my injection pump at 1300rpms. At that point I knew I was getting air in the system.

I had a new Toyota hand pump/ filter sitting on the shelf, along with all new 10mm line. I installed all of them and all the soft lines all the way back to the tank. I installed clear vinyl line between the hand pump and the hard line on the firewall and confirmed I am still getting air in the system.

The 1HZ isn't running bad aside from the noise I heard from the injection pump (around 1300rpms) as I riffle through the gears until the truck has warmed up, I presume after Ive got enough air out of the pump it doesn't make anymore noise.

My question is there another area that I could be leaking air in besides the hand pump and the soft lines? The truck is not rusty and none of the hard lines appear to have any damage.

 

[lowtideride]

 

[lowtideride]

Hard to tell but it was dark and the live action picture turned all the bubbles into cloudiness in the photo.

 

[barrett1]

Hard to tell but it was dark and the live action picture turned all the bubbles into cloudiness in the photo.

Talking about fuel filters. I was just dicking around with my hzj73 in the garage and pumped the fuel filter a few times. Fuel then squirted out of the nipple/petcock at the bottom of the fuel filter for 10 seconds or so. I checked and this valve was fully screwed clockwise in. I was under the impression it would be closed and not let fuel out. Is this something that is faulty and should be replaced? Could it also be letting air suck in If it lets fuel out while supposedly being closed?

 

[DivByZero]

That's busted, should be replaced. That's the drain plug/water sensor, should be sealed tight. It should only let anything out when you loosen it to drain water out of the filter.

 

[Trivver]

Did we end up finding a solution? mine is losing pressure over night too.

 

[RandyMarsh88]

Did we end up finding a solution? mine is losing pressure over night too.

I had a fuel leak on my priming pump. It was easy to spot once I noticed it, little bubbles would form while it was running and the primer pump was wet with diesel. I guess it's a common point of failure.
Unfortunately, I don't think there is a simple answer to this, essentially you have a hole in your fuel lines somewhere... could be anywhere.