5 speed only starts with interlock switch

[St00pkid]

So I finally got my hands on a hardbody, and had to buy it somewhat sight unseen from states away. I got a call the morning the auto transport company was going to drop it off asking me if there's any trick to getting the truck started as they were having issues getting it to start. As I hadn't driven the truck yet I couldn't provide any help with that, so he says he'll call the previous driver who got it onto the transport truck. Fast forward to when the transporter was dropping the car off and I asked him if he was able to get it started and he proceeds to show me the "cool little trick" to get it started.

Essentially the truck will only start if you turn the key all the way to the start position, and then use the interlock switch to actually start it up. As much as it feels fancy to have the 1992 equivilent of a push to start, having to crank the key at the same time turns starting the truck into a very awkward two hand job. I ordered a new clutch safety switch yesterday, so hopefully swapping that out will do the trick but I was wondering if anyone had any insight on this issue in case it doesn't.

[Deerhurst]

Probably just the switch on the clutch pedal.

[YEPEE]

or the little pad that the switch makes contact with..

[PorknBeans]

FYI...

The clutch pedal requires to be pushed to the floorboard to close the switch to complete the circuit to Ground and create the path to the starter.

If you have the switch in your hand. Push the black peg in to hear/feel it click. This is the closing of the switch and completes the circuit to Ground allowing the truck to start.

It's the built in safety feature.

[St00pkid]

Turns out it was the little pad that makes the contact with the switch. Previous owner replaced it with a plastic fastner that had worn through so it was no longer making contact. For the time being I've replaced it with a new larger fastner until the rubber replacement comes in. Luckily I was able to cancel my order for the replacement switch before it shipped.

Thanks for the help guys. Now I just gotta get to the bottom of the god forsaken egr code so I can get it inspected...

[PorknBeans]

Good find!

That little rubber “nub” fell out of my pedal and illuminated all 3 brake lights on my truck. It was cool how it lit up my garage with the red glow! I didn’t drive it until it was fixed.

I installed a small metal square I found on the floor.

The EGR System valve can be tested with a vacuum pump. I use a MityVac. It can be blown out to clear the carbon and/or dust/debris caught in the open housing design and cause the valve to “stick” and not operate correctly. Use a vacuum pump and disconnect the small hose from the solenoid and connect to the pump. Creat the vacuum and see if the valve lifts up. If not, the valve might need a good once over to clear out any sand or debris that’s causing it to fail. Also, rev the engine to 3,000 rpm and see if the valve lifts up and then drops when the rpms drop. This tells you the valve is good. Not good if the valve doesn’t lift or drop under hand vacuum or engine vacuum. Not sure if you the BPT valve. Block one port of the 3 ports with a cap or your finger. Disconnect the small hose from the solenoid and apply vacuum from the pump to the bottom nipple. There shouldn’t be any drop in pressure with this test and air should pass through the 2 ports freely. It’s in the service manual. Also, the PCV vavlve should have vacuum when the hose is disconnected. If not, replace the $5 valve.

[St00pkid]

Thanks so much for the ideas on the EGR valve. I tried some of the trouble shooting you suggested. First thing I did was have my fiance start the engine and rev it up to 2000 rpms, no movement on the EGR diaphram. Then up to 3000, no movement on the EGR. Then up to 4000 and (drum roll).... no movement. Then I tried the other trick I read about and manually depressed the EGR while the engine was idling. It definitely stumbled a bit and wasnt having a good time, but it didn't stall out on me. I kept it depressed for a solid 10-15 seconds and didn't stall. I'm not sure if I should've kept it for longer but it didnt seem like it was making any progress towards stalling.

The only thing thats throwing me off a little bit is after pulling the EGR I tried the method of depressing the diaphram and plugging the vacuum line and it held the diaphram up and was holding the vacuum. I also took a look at the ports on the EGR and they're blackened with carbon but theres definitely no build up causing a blockage on the ports. I'm not sure if theres another spot that the carbon could build up to create an issue.

I'll hopefully be picking up a vacuum pump later this week so I can diagnose some more, and I'll give the EGR assembly a good cleaning. I was thinking of pulling the metal tube that connects to the exhaust as I've heard that can get pretty clogged, but for the life of me I can't get it disconnected from the exhaust. If anyone has tips besides growing extendo arms it would be greatly appreciated.

And just some additional info, the EGR definitely doesn't look oem, and the previous owner must've replaced most, if not all, the vacuum lines pretty recently. All the hoses are in good shape and bright red.

Any tips on where to go from here? Or should I just wait until the EGR is nice and clean and cross my fingers that it does the trick?

[PorknBeans]

If the engine is idling and you’re pressing up(simulating vacuum). Then the truck should start to stumble and then immediately stall. If it doesn’t stall and you can keep the valve fully up by hand for more than 5 seconds and the truck doesn’t stall out or you can just push up fully and release the valve severally times without any stalling. The EGR valve is either clogged or faulty. But it should definitely stall out the engine when idling. The valve should also lift up(that’s engine vacuum lifting the valve to allow exhaust back into the combustion cycle) when the engine is revved to 2000, 2500, 3000 rpm. If not. It’s clogged and/or faulty.

I wouldn’t worry about the exhaust tube. Amazon sells an easier one to install. Straighter with less bends and a direct replacement.

No easy way to remove that tube. High heat exposure “welds” the threads together. PB Blaster and vise grips very tightly clamped on the hex connector worked for me while gently rocking the tube connector back and forth to break it loose. It will not be easy to remove! But if you can get it to move. Move it the other way and spray the threads with PB Blaster or penetrating oil. Then turn the connector the other direction and then spray it again. Spray. Turn. Repeat until it comes all the way off.

But do the valve first and check for any changes. Leave the tube for now. Unless it’s cracked or damaged and leaking.

[St00pkid]

Alright will do. Thanks bro, I'll update when the EGR is cleaned and back in. Lets see if I'll need a new one or not