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| SJ51T won't drive up hills forwards https://www.auszookers.com/forum/viewtopic.php?f=5&t=57573 |
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| Author: | turbo510 [ Mon Sep 11, 2023 4:40 pm ] |
| Post subject: | SJ51T won't drive up hills forwards |
Hi all, I have an SJ51T as my farm hack. I live in Gippsland and own a very steep property. The problem I have is my Suzi won't drive forward up the hills on my property. It will reverse up the hills no problem but it wont drive up them forwards. I have pulled the fuel tank out and cleaned it, replaced the filter multiple times, replaced the mechanical fuel pump, and added a secondary electric fuel pump. The carby looks to be in good condition with no external leaks. The next step as I see it is to rebuild the carby but I don't want to throw money in the wrong places. Any ideas on what might be causing the problem? A pic of the problem ute |
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| Author: | Brenno [ Mon Sep 11, 2023 4:43 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
What are the symptoms? Stalling out? If you put the clutch in will it idle and rev etc? Likely carby but need a bit more info. |
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| Author: | fordem [ Mon Sep 11, 2023 7:58 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
What are the symptoms when it won't drive? |
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| Author: | turbo510 [ Tue Sep 12, 2023 9:50 am ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Symptoms are like it is running out of fuel under load. It just stops pulling in gear. Put the clutch in and it will idle but it won't run under load. Fuel level in the tank has no impact on the issue. I have also replaced all the fuel lines, hard and rubber. To give you an indication of how steep the property is I can only use first gear in 4 Low. It won't pull second up the hills. I've got a reduction transfer to go in it but want to sort out the running issue before I change the gearbox, transfer and diffs for the replacements I have here. |
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| Author: | Gwagensteve [ Tue Sep 12, 2023 12:52 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Sounds like it could be an ignition problem to me. The limiting factor for a basically standard sierra is traction, not engine torque. Sounds to me like the timing is retarded/the vac advance isn’t working/ there’s a really weak spark and that’s resulting in no torque or drivability under load. |
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| Author: | turbo510 [ Tue Sep 12, 2023 3:58 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Gwagensteve wrote: Sounds like it could be an ignition problem to me. The limiting factor for a basically standard sierra is traction, not engine torque. Sounds to me like the timing is retarded/the vac advance isn’t working/ there’s a really weak spark and that’s resulting in no torque or drivability under load. It used to make it up the hills in first gear no worries, something is obviously deteriorating rather than an instant failure. It's never had enough grunt to pull second gear. My place is steep. Not much will get up it other than the Suzi without ripping the place apart I've checked the timing and it is set right, haven't checked the vac advance but I will have a look. Surely if the timing/vac advance was out it wouldn't be directional. I can reverse up the steepest hills on my place, just can't drive up them forwards. |
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| Author: | Gwagensteve [ Tue Sep 12, 2023 6:01 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
I’m trying to determine if the car is generally down on power. Reverse is lower than first gear and there are other potential factors (weight distribution and it’s effect on traction) Sierras have high enough torque to weight that they don’t run out of puff in 1st low unless they are diff locked (and therefore generate more traction and therefore more load on the engine) are very heavily laden, or run tall tyres with standard gearing. I know private properties can be steep but 4wd tracks can also be very, very steep, so steep that an unlocked sierra on smallish tyres can’t climb further than its wheelbase without using lots of momentum. With open diffs and on an unpaved surface they will wheelspin before they bog down assuming revs are high enough. Of course if if the terrain is very rough it’s not possible to keep revs high enough as the car is moving too fast, but that’s mostly a problem once the car has locked diffs- with open diffs the car will wheelspin which keeps the revs up. This all might sound irrelevant but it’s important to try and work out if there has always been a problem or if it’s new. Some other ideas: Secondary not opening/secondary jet blocked. (Note, a blocked idle jet is most common as it’s the smallest, you don’t have that problem) choke stuck on, fuel pickup damaged/holed/ cracked, an air leak in the fuel system somewhere, Normally I’d say fuel pump for sure. Sierras are notorious for dumping the float bowl into the carb on steep climbs but I don’t believe that’s the issue because it takes very specific conditions for them to do it. Typically the car has to be drivers side low and climbing very steeply then encounter a bump. The engine will run for a second then die. It will not restart or idle until the car is back off the side angle. If the car is low on the passenger side it will run regardless of angle and re start, even if the car is completely on its side. I have seen this many times, it’s the case with any sierra with a stock carby. If the car is fairly level left/right they will run at basically any angle when climbing or descending. So, I’m leaning toward the problem being a lack of torque through a combination of factors (possibly ignition related) rather than a single carburettor issue because the car as shown should run out of traction before it runs out of power in low 1st or reverse. |
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| Author: | turbo510 [ Wed Sep 13, 2023 11:14 am ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
I appreciate the help. I did some more testing yesterday and it is definitely looking fuel related. If I try to drive forwards up the hill on the lowest throttle opening possible it makes it further than if I use full throttle which indicates to me it is draining the fuel bowl. In reverse it will drive up the hill at low throttle or at full throttle. If I stop and clutch in quick enough when it starts to lose power it will keep idling, give it 30 - 45 seconds and then it will go again till it loses power, and so on. The motor in it is a little tired with 150 psi across cylinders 2 - 4 but only 120psi in no. 1 tested dry. It is also due valve seals as she smokes after going long downhills with closed throttle/high vacuum. Maybe it is time I bought the neighbours Baleno and upgraded to 1.6 and EFI. Once it dries out a bit I can use my Patrol without ripping the place apart. This time of year it is too wet and does too much damage. |
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| Author: | shep [ Wed Sep 13, 2023 12:59 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Is it definitely the stock carby? |
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| Author: | turbo510 [ Wed Sep 13, 2023 2:43 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
shep wrote: Is it definitely the stock carby? It looks the same as the one in the workshop manual I am using |
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| Author: | turbo510 [ Tue Oct 31, 2023 8:28 am ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Pulled the carby down on this to rebuild, unfortunately it has been well fingered by a previous owner. Stripped screw heads, stripped threads, missing screws, butchered jets. I'm surprised it ran as well as it did. Replacement carby ordered - I'll update this thread once it is fitted. |
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| Author: | turbo510 [ Tue Jul 30, 2024 3:37 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Long time no update - but I wanted to update this in case it helps others. Fitted up an EBay carby to replace the butchered original and still not a lot of luck. Ended up going to an external fuel system (motorbike tank gravity feed strapped to the roof) and it was running fine. Figured it had to be part of the fuel system, checked in the tank again and it was fine. Removed the fuel line to the mechanical pump and the electric pump up the back was pumping as it should. Reconnected it to the new mechanical pump I had fitted and there was almost no flow. So it turned out the new mechanical fuel pump I had fitted was a dud. Bypassed it and just left the electric pump on it up the back and it is running sweet now. Moral of the story - don't take it for granted that new parts definitely work. Still smoking away as I haven't done the valve stem seals yet but I stumbled on to a Baleno stashed behind the neighbours old dairy. Fired it up and it runs well so that will be the donor for my ute. Also picked up a wide track roller so it will be getting wide track diffs and I have a reduction transfer and AC to fit. Now just to find the time to do it all |
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| Author: | fordem [ Tue Jul 30, 2024 8:14 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
There wouldn't normally be an electric fuel pump on that. |
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| Author: | turbo510 [ Wed Jul 31, 2024 10:43 am ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
I added the electric pump, I mentioned it in the first post |
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| Author: | Andygoodbloke [ Thu Aug 01, 2024 7:01 pm ] |
| Post subject: | Re: SJ51T won't drive up hills forwards |
Check the float level of the feeder bowl. This is the float that opens up to more fuel when it gets empty, if the float is too low the vehicle basically runs out of fuel and can't keep up under load. If you strip the carb down you will see the float and if un done a needle point valve connected to the float. Basically give the float a bend so it sits higher, kind of like moving the float in the toilet cistern for more or less water in the flush. If the needle point valve is dirty clean it. Can't guarantee it is the solution but is one worth checking. Also look at the angle the float sits at before you start so if all else fails you can return it to where it was. Hope it helps |
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