Gauge issues and Vacuum leak (2 problems)

[blue78]

I apologize up front for the lengthy post. Cliff notes version is the gauges aren't working and I have checked all obvious sources and it dies when I put it in gear. Read on for the full version.

So I have been getting kicked in the pills over the past two days with two separate issues that are equally frustrating.

The first is the one that is driving me crazy because I have read about 20 threads on here about gauges not working and have tried to track down each of the issues that were mentioned and I am still getting no love.

I tested the IVR and it was only putting out 2 volts so I went and got a new one, that one was putting out 12 volts so I checked the ground. I grounded direct to the firewall (there is a grounding strap from body to frame, frame to block, and block to battery) and still no voltage drop. So I put the old IVR back in and tuned it and boom, 5.8 volts after I adjusted it!! Still no dice on the gauges though.

I ran a clean 12 volts to each of the gauges and they all peg out to full so they work. I also ohmed out all of the wires and no shorts there. The sending units for oil and temp ohm out at 13 ohms, fuel sender I didn't check because I put a brand new one in (I know it could be faulty out of the box but I think I have another issue) so I am guessing that works. My next step is to order sending units from one of the bronco houses because someone mentioned that the gauges work with specific sending units and the bronco shops sell you what you need.

I am at a loss at this point, I just threw it all back together and hope that the electric gods sort it out. I have bigger fish to fry anyway, which brings us to problem two:

The truck dies when I put it in gear. This is a freshly rebuilt 302 for the V8 swap and a C4 that I was told was good to go (I pray that it's not the issue) so I figured it was a vacuum leak. I got out the carb cleaner and found that the carb had a leak at the base. Put a new carb seal on and still dying so I got a new carb. That helped but then I sprayed it to check and found that the intake seal to the heads is also a source of vacuum leak, ran a bead of RTV and it is so close but there is still something I am missing. I capped off the brake booster line and still no love. I am out of possible vacuum leaks, I think, so what am I missing? I disconnected the drive shaft and it is spinning the output shaft on the transfer case in drive and reverse, but once everything is hooked up it dies. My two big fear are a crack in the manifold that I can't see or a locked torque converter.

This is the end of a very long an expensive road and all I want to do is drive this damn thing. I will post a full build thread once I have it running and driving, but I need to clear this last hurdle to get there.

What am I missing, Bronco Gurus?

Kyle

 

[B RON CO]

Hi, the quick test for the oil, temp and fuel gauge is to ground the sender wire and the gauge should go full sweep.The amp gauge is not on the IVR.
I don't think a bead of silicone would seal the gasket. I don't know if you have an aluminum intake, but they are known to be leak prone between the manifold and head.
I would put a vacuum gauge on it.
What is your idle RPM?
Good luck

 

[blue78]

Hi, the quick test for the oil, temp and fuel gauge is to ground the sender wire and the gauge should go full sweep.The amp gauge is not on the IVR.
I don't think a bead of silicone would seal the gasket. I don't know if you have an aluminum intake, but they are known to be leak prone between the manifold and head.
I would put a vacuum gauge on it.
What is your idle RPM?
Good luck

I'll try grounding those tomorrow, if that pegs them then where do I start looking?

It is an aluminum intake. The silicone has taken care of a couple of the places I was getting a leak so I just ran a bead and will let it dry over night. I figure if it doesn't work then I'll pull the manifold and see what's up. The guy who built the motor offered to get me another manifold if that turns out to be the issue. I'll save that as the nuclear option.

Idle is set at 1100 right now. It should be pulling 14" vacuum, right. That is what I seem to remember reading somewhere.



Thanks for the help.

Kyle

 

[B RON CO]

Hi, unless you have a wild cam, the idle should be no more than 700 or 750 RPM, and @ 17 or more inches of vacuum. The vacuum should be very steady.
Good luck

 

[blue78]

Hi, unless you have a wild cam, the idle should be no more than 700 or 750 RPM, and @ 17 or more inches of vacuum. The vacuum should be very steady.
Good luck

Ok, I'll see what I can get going tomorrow. Thanks again.

 

[66broncoCT]

Yeah a bead of silicone wont fix intake manifold gasket leaks. You might've stopped the leak up top but you probably still have a vacuum leak below sucking air from the lifter valley. Need to pull the manifold and replace the gaskets. High idle could be from the vacuum leak or a misadjusted carb.

 

[Rustytruck]

Try 900 rpm at idle in park which should get you 700 or so in drive.

Hook up a vacuum gauge so you can see actual changes when you searching for vacuum leaks. Silicone the intake manifold wont solve the problem if gaskets have failed. They fail as much on the bottom as they do on top. Make sure your using reinforced intake gaskets.

As for the c-4 there is a vacuum modulator on the tranny it may have one or 2 vacuum ports on it. check and see if the manifold vacuum is getting there. Check that there is no tranny fluid in the vacuum line. If you have a dual port vacuum modulator the fitting closest to the back of the tranny is the one running off manifold the smaller one closest to the transmission pan is for emission control and needs to be hooked up to work with the emission system parts. if you do not use emission parts then leave this port open and cap the vacuum line going to it.

If you have the stock 2 barrel carb with the preheat tubes from the exhaust manifold to the choke if you don't run the tubes you will have a vacuum leak at the choke.

Check the vacuum canister at the distributor make sure it doesn't leak. and make sure it is hooked up to ported vacuum at the carb. At normal idle speed there should not be any vacuum at the canister if hooked up properly.

 

[DirtDonk]

Was this the engine originally from the Bronco and you just had it rebuilt? Or is it a donor?
If original, are the sending units the ones that came in it and they worked prior to the rebuild?
Just wondering about the 13ohms when cold, since that should have the gauges pegged, or at least very near the top of their range.

But the grounding test should let you know for sure. If you ground the sending unit wires out at the senders themselves, and the gauges peg with the key in the RUN position (the key is in RUN, and not ACC, just to be sure. Correct?) then the sending units are bad.

Did you do other stuff to the truck at the same time as the engine? Such as new paint on the dash for example?
Is the ground wire you used to test the IVR still in place? The gauge cluster needs to be grounded, but that's more for the lights and the IVR itself, not the gauges themselves. So if you are seeing that 5.8v output pretty consistently and grounding the senders pegs the gauges, everything should be working!

I hope it's something simple anyway. Quite the mystery otherwise.

Good luck.

Paul

 

[DirtDonk]

Oh, and where is your vacuum advance connected?
If it's not on the ported fitting on the carb and is getting full vacuum, that might explain the high idly and the dying when in gear issue.
Easy enough to test anyway. You can even leave the vacuum advance off completely for testing purposes.

And I sure hope the cam was broken in before all of this by the rebuilder. If not, were you able to get it running well enough to keep it reved up to 2500rpm for an extended period of time (at least 20 minutes) for the break-in?

Paul

 

[blue78]

Ok, so I set the idle at 900 RPM and it still runs fine but with the same issue. I can't get my vacuum gauge to work but I'll figure that out later. I have taken a video of the issue I am having and I am fairly certain that either the manifold is warped or the seals are garbage. I have unplugged and capped every vacuum line from the mainfold and still no dice. I have taken a video to show you guys what I am talking about and I am guessing you'll all say bad manifold, but take a look and let me know.

video link https://www.youtube.com/watch?v=YrbR9AU0OCk


To answer Paul, this is a rebuild out of a donor, it is a 93 roller motor for the V8 swap and it is going in at the end of a full rebuild. Almost all metal is new but the dash was in good shape (don't mine the PO's hacky radio hole). My builder broke it in on a stand and I can get it running like a top until I apply load. I was on the phone with him tonight and after watching the video he is going to swap me out another manifold at Ford Nationals this weekend, which is a double dick punch because I was really hoping to drive her up there.

The gauges: I grounded out all of the sender wires and now I am confused. The water temp was first and it went up to about 170 and held there. Then I tried the oil pressure and it didn't move at all. Next was fuel and it would "tick" up, almost like it was fighting resistance to move, but it only made it to about a quarter tank and stopped. That makes me think IVR is not doing its job, right?

I'm getting to the point where I am ready to spend my way out of this problem and replace the whole gauge head and senders but I'm sure the collective knowledge on here has a smarter solution, what say the brain trust?

And thank you all for the quick and thorough responses, I truly appreciate you guys taking the time.

Kyle

 

[DirtDonk]

Ok, so it's not the senders at this point. Even if they're indeed out of spec, they're at least not causing the problem.
The fact that the gauges did not climb much means that either the IVR is not putting out enough voltage, the wiring is bad, the grounding of the gauges is insufficient, or the gauges themselves are bad.

You can test the voltage theory easily enough (like you already did before, but different) by taking your measurement with a volt-meter out at the end where the sending unit is.
If you get that same pulsing voltage that looks to average out at or near 5-6 volts, your wiring between the senders and gauges is fine. At that point the gauges are suspect.

The good news is that you can have yours refurbished by member Fallingdown (you may have seen his thread in the Vendor section?) or you can buy them brand new now too.
But we won't go there just yet. A few more checks and a little more hair-pulling first.

But right now, a pertinent point. Did you say what year your Bronco is? If it's a '70 or earlier model, check your firewall plugs. Those are the two large rectangular connectors near the throttle linkage on the firewall. They're a common resistance issue and could be suspect as well.
Sometimes simply pulling them apart and then putting them back together again is enough to get rid of some electrical gremlins temporarily at least.
Well worth a try.

Then again... It's a Bronco so it's never that easy!%)

Paul

 

[DirtDonk]

Holy moly! Just watched the video and yeah, I'd say you found a leak. More like a leak-and-a-half!
Nothing else down that way that we can't see though, right? Like an open 3/8" PCV port on the side of the throttle body, or anything like that?
Just wanted to make sure, before you got to taking things apart again.

I wonder if the builder ended up using the gasket that everybody around here has had bad luck with when they tried it. I can't remember what it was, but lots of members have discussed it. Fel-Pro something or other.

Good luck.

Paul

 

[DirtDonk]

Oh, and now I'm completely jealous too! My new favorite Bronco color.
Is that what? Lunar Green, or whatever they called it for each year? Maybe not the same as the one they had in '77, but still one of the nicest Bronco colors around.
And there are quite a few!

You got more pictures around here somewhere yet? A build thread I missed maybe?

Thanks

Paul

 

[blue78]

Holy moly! Just watched the video and yeah, I'd say you found a leak. More like a leak-and-a-half!
Nothing else down that way that we can't see though, right? Like an open 3/8" PCV port on the side of the throttle body, or anything like that?
Just wanted to make sure, before you got to taking things apart again.

I wonder if the builder ended up using the gasket that everybody around here has had bad luck with when they tried it. I can't remember what it was, but lots of members have discussed it. Fel-Pro something or other.

Good luck.

Paul

I read a couple reviews on Fel-Pros that were bad and some that were good, I'll get a new manifold and gaskets and see what's up. The carb is brand new (one of my troubleshooting techniques is to start with the most expensive possible fix) and all of the ports are capped so at this point I think it has to be that manifold.

I'll keep playing with the gauges, at this point I may just buy a new one at the Ford Nationals this week if one is sitting around.

As for the Bronco itself, you have not missed anything, I have been keeping it under wraps on here until I can do a full build thread post. I am horrible at keeping up with them on here so once I am done I will do the full build (actually went through it twice in 13 months) with pics and details.

It is a Lunar Green 68 Half Cab, I was debating on going with that or Brittany Blue and since this was the original paint code it won. I have to say I am a huge fan of it too now that it is on. I did a couple things with this one that I am pretty proud of so I am excited to share the build, but until this thing can run and drive it's not done.

Wild Horses is responsible for about half of the parts on this build so I'll be sure to tag you guys once it is done.

Kyle

 

[DirtDonk]

Fantastic. Can't wait to see any more pics and a write-up when you're ready.
I think Brittany is a great Bronco color. We had an original from '70 or '71 at our gathering the other night.
But other than maybe Boxwood, the Lunar Green is one of the very best.

And thanks for the support! We had three or four Special Decor '77's at our first Roundup at WH three years ago. If I remember, one was Lunar Green.
And one Lunar Green Ranger that was to die for!

Very cool. Looking forward to more.
Have fun.

Paul

 

[TOOLMAN]

I had a gauge problem like this a couple years ago. I was on a really tough trail and lost all my gauges about mid-trip. Got home and checked the fuse. It was blown so I replaced it. I thought I was good until I started it, put it in reverse and the gauges went dead again. What happened was my reverse lamp switch wire got pinched, shorted, and blew the fuse (apparently was on the same circuit as the gauges on the Centech loom).

It seems like the gauges are getting no power/have a bad ground. Probably no ground. I think I read that the gauges came up a little when you grounded them except for oil pressure, which wouldn't if the engine isn't running. Doesn't the cluster have to be attached to the dash for ground? I may have read that once, but someone can correct me.

 

[blue78]

I had a gauge problem like this a couple years ago. I was on a really tough trail and lost all my gauges about mid-trip. Got home and checked the fuse. It was blown so I replaced it. I thought I was good until I started it, put it in reverse and the gauges went dead again. What happened was my reverse lamp switch wire got pinched, shorted, and blew the fuse (apparently was on the same circuit as the gauges on the Centech loom).

It seems like the gauges are getting no power/have a bad ground. Probably no ground. I think I read that the gauges came up a little when you grounded them except for oil pressure, which wouldn't if the engine isn't running. Doesn't the cluster have to be attached to the dash for ground? I may have read that once, but someone can correct me.

I do have a Centech that I didn't install myself so I guess I'm going to have to start hunting at this point. I am going to check voltage at the sensor and make sure the gauges aren't junk, but after that I may just rewire each one individually and see if I can isolate a problem that way. Then fun never ends.

Kyle

 

[blue78]

UPDATE: Tonight I switched out the manifold and gaskets and she runs and shifts into gear without dying!! since I swapped both out I don't know if it was the Felpro gaskets that I read some bad reviews on or a warped intake. Either way, it fired right up, went into gear and held steady.

Tomorrow we test drive!!!

Oh, and the gas gauge started working out of nowhere. So now I get to chase down whatever bare spot in the wire is causing that. Once I have her driving I will do a full build thread, I am excited to show her off.

Kyle

 

[blue78]

Well, apparently I was high last night because today I put it into gear and she died again. I almost put a hole in the wall. Same issue, I spray the manifold with starter fluid and she dies. Only thing that changed between last night when it ran in gear and today is I filled the coolant and set the timing today before putting it in gear.

That made my motor guy think that I stabbed the dizzy in a tooth or two off. I sent him a pic and he said it is way off. My question is, is it possible for a motor to run amazing at 8-10 degrees advance a tooth off and have that cause a vacuum issue?

I'm at a loss at this point, all I can think is that I have a bad head. They were rebuilt but I don't know if they were fluxed for cracks and that is my one armed man right now.

I added pics of where the crank is at when the rotor is pointing at the #1 wire on the cap.

I told my friend that I was just going to yank the motor an get the 347 I should have got in the first place but I would have to sell a kidney at this point.

 

[B RON CO]

Hi, well it does look like the ignition timing is off.
The standard Ford factory would have the vacuum advance cannister in front of the engine and the rotor pointing more or less at 1:00, towards the master cylinder.
I would bring the mark on the balancer up to # 1 tdc and see where you are at.
If the picture is #1 tdc, that explains why the distributor is twisted clock wise so much.
I would probably gently lift the distributor and turn the rotor counterclockwise 1 tooth ( maybe 2) and see if the rotor lands at 1:00 o'clock with the timing marks lined up and the vacuum advance cannister in front.
Also make sure the firing order corresponds with a Ford diagram, with the rotor pointing right at the #1 wire on the cap. It is a good idea to mark the distributor body with a sharpie where the #1 wire on the cap is so you can easily see the spot with the cap off.
Good luck