Lost my idle and obvious fixes didn’t work. Need help. (1 Viewer)

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Buena Vista, CO
Here’s my story... 1974 FJ40. Owned it for 15 years but it sits for 8 months every winter, and then driven only about 15+ short outings each summer.
I know, that’s a sin and I may be paying for it now.
So two weeks ago it fired it up from it’s deep sleep and it ran fine as usual. After 3-4 days of normal performance, it suddenly won’t idle. This happened instantly. One minute it idles, then it doesn’t. It runs normally if I give it any pedal but dies instantly if foot leaves pedal. So I search Mud extensively and come up with two big suspects: the idle solenoid doesn’t give me that click, and I discover the PCV hose is cracked and likely leaking creating a vacuum leak. Got to be one or both of those right? So I Installed a NEW idle solenoid ($185 from SOR - ouch - and they didn’t even include a new gasket!), and replaced everything new on the PCV line including valve, hose and grommet. After all of that - it still won’t idle. So time for a stiff drink and an appeal to the MUD brain trust.

Before I started any repair work I noted that the sight glass in the carb showed fuel half way up - good. But now, the bowl is either totally full or empty, though it can’t be empty because the accelerator pump will squirt gas. I check the distributor to see if it might be loose, but that was solid. I don’t think a vacuum gauge would help if it doesn’t idle. Soooo, what would you guys suggest I check next?
 
Joined
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Buena Vista, CO
Your sure you have power to the idle solenoid? If so I’d blow out the fuel lines and try it again.
W
No. I need to check that. I’ve done all my tests on the solenoid with direct connections to the battery. Duh.. I never checked the power wire to the solenoid. ....Give me 12 hours and I’ll have the answer. Great insight.
 

Pighead

Stop calling it an FJ
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Does your new solenoid click with the ignition turned on? Can you make your old solenoid click if you give it 12 volts (neg to the body and pos to the wire)?
You've got two solenoids now right? If you cut the rod off the old one and screw it back on to the carb you can run it, you just have a disabled solenoid.
If it idles, you don't have power to the solenoid.
 

65swb45

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Disconnect the brake booster from the intake manifold and cap the manifold. If that makes a difference, you have a bad booster.
 
Joined
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Ok, I’ve done several tests which I’ll list. These will also answer your questions.
I isolated the brake booster and this didn’t fix it.
I checked power to the new idle solenoid and I’m convinced it’s working properly. It’s got voltage and I get a solid click when the ignition is turned on. And before I installed it I confirmed the small rod coming out of the solenoid is retracting when power is applied.
Pig head - it WILL idle when the choke is pulled. The more I pull the choke the faster it runs with having to depress the accelerator.
I get a very good / steady fast idle with the choke pulled about 1/2 to 2/3rds. At this fast idle speed I put the vacuum gauge on it and got 13 inches, BUT factor in that my elevation is 9000 feet. Even still, that seems too low. I’ve visually inspected all the vacuum lines but maybe I should spray carb cleaner on connections to see if I can pick up a leak.
I also confirmed that the fuel level in the bowl stays about half way up when the truck is running.
But the problem remains - with the engine fully warmed up and no choke, it dies instantly when you release the accelerator.

Suggestions please, and thanks for your help.
 
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Oh and that 13 inches of vacuum was with the air cleaner off. Not sure if that makes a difference.

if you guys think I need to search for vacuum leaks, let me know your preferred method and locations to check. I’m familiar with the vacuum 101 post in the FAQs but I’ll do some more research too.
 

Spike Strip

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Roughly, engine vacuum will fall 1 in for each 1000' of elevation, so 13 hg isn't bad.

Since everything else seems to check out, prolly crud in the idle circuit or maybe slow jet.

Time for a rebuild?
 

77mustard40

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Since it’s a sitter I’m thinking you’ve got some crap in your fuel line or a Vac leak, 13 sounds low to me. iIRC I’m up around 18.
 
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I'd say your vacuum sounds good. With a high idle at 9000' I'd say 13" is pretty good. I'd check for major vacuum leaks at your intake gasket, carb gasket, etc. Set the choke just enough for it to idle, spray the area with carb cleaner, and listen for rpm to increase. When it increases, there be your leak. If all checks out. You may be looking at disassembling and cleaning the carb.
 

77mustard40

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On mine it leaked at the intake/exhaust manifold gasket, took a couple swings to fix it. Good luck on your hunt for the prob
 
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Thanks guys. I’ll go with the consensus here and first do a though search for any vacuum leaks, although on balance I don’t think my vacuum is that bad given my altitude and the condition of my truck. But I’m going to order a carb rebuild kit too. That can’t hurt and it might be the source of the problem. I will report back on how this plays out.
 

Dizzy

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My 2F is running awesome at 13in at 600rpm, 6,800'

My guess is that it is carb related, unless you have one of those headers that requires hacks.
 

4Cruisers

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When tuned and adjusted, the vacuum on my stock '76 FJ40 with ~66,000 miles is ~15.2" Hg at 7,240'.
 
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Picked up my first cruiser a few weeks ago. This thread caught my eye because I was having similar issues. First, the PO had patched two vacuum lines together, they'd come apart and it wouldn't start. Picked up a piece of new tubing and fixed that.

Second, my throttle cable was getting stuck, so when I pushed the clutch in or came to a stop, the engine was rev'd out. My "temporary fix", was to loosen the throttle cable line at the carburetor because I thought it had too much tension. For good measure I ran a nut and spring from the top of the valve cover to assist pulling the slack out of the throttle cable at the carb. It ran great that afternoon, but the next morning on the way to work, every time I came to a stop the engine died. It would crank right back up and run as long as a kept pressure on the accelerator, but would not idle. When I got home I added more tension to the throttle cable, idled fine in the garage, went to pull out onto the street, it died again.... Tightened the throttle cable up a little more, and it has been fine the past few days.

I need to replace the throttle cable, but until then I'm back on the road.
 
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Does it happen to be a California model with an EGR valve?
I’m pretty sure the truck is a Federal, not California version. The sticker under the hood mentions complying with Federal standards and no reference to California. BUT it’s had some modifications that puzzle me. It has headers and the front crankshaft pulley has slots for 2 belts, but there’s only one now. The intake manifold does have small plugged ports for each cylinder where something could have been connected, but maybe they used the same manifold for all versions and put plugs in those holes when not needed.
I’ve ordered the carb rebuild kit and hope to get this done in a week or so.
 

Pighead

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Those plugged holes are in the head, not manifold. They were for the air rail.
the extra groove in the pulley was for the smog pump belt.
So, it's been de-smogged. Perhaps not well.
How about some pics of the engine?
 

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