Weber Woes

[baseballguru44]

Apologies in advance for the long post. Just trying to describe my situation in as much detail as possible.

 

I own a 1985 Nissan 720 Truck with the Z24 4-cylinder (two plugs per cylinder). I just put in a rebuilt engine and have basically replaced, swapped, or deleted everything in the engine bay. Everything emissions-related is removed. No EGR, vacuum valves, canister, etc. The only vacuum running from the intake is to the brake booster and the distributor vacuum advance.

 

I decided to replace my factory Hitachi carb with a Redline Weber 32/26 DGEV. All components were purchased through All Automotive in California. They are authentic, made in Spain.

 

First off, I do not have any vacuum leaks. Everything is properly sealed or blocked off. I have checked. My starter and my battery are good. Ignition coils/plug wires/firing order is correct. I have a fuel pressure regulator set at 3 PSI. I have tried 0.5-5, and 3 seems to do the best. I have experimented with setting my timing anywhere from 2-10 degrees. The factory timing is 3 degrees at 800 RPM. It seems so far to do best around 5-6 degrees.

 

I have several noticeable problems. First, when turning over to start, it begins to "lock." Appeared to be getting too much fuel. Once it finally starts, any normal amount of gas would cause a backfire through the carb and release gasoline out the top. Please note, when driving down the highway, it runs and drives fine. The main issue is at idle under 1000 RPM.

 

I purchased the 701-DGV4 jet kit and began experimenting with different idle jet sizes. Below is a list of the sizes experimented. The idle screw was always set at 1 1/2 turns, where it’s supposed to be. The timing was around 5 degrees on all these swaps.

 

Stock: Primary 60, Secondary 55

1st: Primary 65, Secondary 55

2nd: Primary 65, Secondary 60

3rd: Primary 70, Secondary 60 (mixture screw at 7/8 turn)

4th: Primary 65, Secondary 60 (mixture screw at 1 1/4 turn)

5th: Primary 60, Secondary 60 (mixture screw at 1 1/2 - 1 3/4 turn)

6th: Primary 70, Secondary 55 (mixture screw at 3/4 - 7/8 turn)

Final: Primary 70, Secondary 60 (mixture screw at 7/8 turn)

 

It seemed to do best at 70/60. Sitting and idling, it would only backfire and die with sharp acceleration. But it still backfires out the carb. I went to drive it at those settings, and it did decent, but died on takeoff several times. Additionally, when I was driving in 3rd/4th gear, put it in neutral, allow the RPMs to fall, it would die, and refuse to start again. Had to dump the clutch to start again.

 

After discussion with other owners, contacting Redline multiple times, and experimenting/checking everything I could think of, I don't know what else to do. The only thing I can think of would be a potential float problem. What else on a brand new carb? Please, any advice would be much appreciated. I'm at my wit's end.

[datzenmike]

The Z24 is notorious for blowing the head gaskets at 100K. Back firing out the intake might be a sign of this. But lets assume not for now and hope for the best till we know different. The preventative measure for a blown head gasket is to re torque the head bolts to assure that they are properly clamping down on the old gasket. Do this in the morning after the engine is completely cold. Loosen only ONE bolt and immediately tighten with a torque wrench to 60 ft. lbs. Only then move to the next bolt. Done this way you can do in any order you choose.

 

 

Warm the engine up to operating temperature and set the valve lash to 0.012" on all. A tight valve might do this. Cost's nothing for parts too.

 

A cracked distributor cap, bad insulation on the plug wires, carbon tracking on the cap rotor or the coil tower might also cause a back fire. Check and clean plugs while you are at it they must be NGK BPR6ES intake and BPR5SE exhaust side. See if any old plug is different looking than the others.

 

 

At some time do a compression test. If one cylinder is down an exhaust valve may be burned or if two adjacent cylinders are low the gasket might be blown between them.

 

 

Get that head re-torqued ASAP because if it hasn't blown it WILL blow and it's over due.

I would set the timing to 3 degrees for now till this is sorted then you can experiment.

[NC85ST]

Almost sounds like timing. You might want to check that it’s set correctly. Quick check would be to have someone try cranking it while you adjust the distributor one way then the other. If you can get it to spin easier, then you know it’s the timing. Sounds like the timing is retarded to much.

[datzenmike]

3 degrees BTDC is correct.

[Charlie69]

Back firing through carb is usually timing.  Did you install new cap, rotor, plugs, and wires?

Edited January 13, 2021 by Charlie69

[baseballguru44]

3 hours ago, datzenmike said:

The Z24 is notorious for blowing the head gaskets at 100K. Back firing out the intake might be a sign of this. But lets assume not for now and hope for the best till we know different. The preventative measure for a blown head gasket is to re torque the head bolts to assure that they are properly clamping down on the old gasket. Do this in the morning after the engine is completely cold. Loosen only ONE bolt and immediately tighten with a torque wrench to 60 ft. lbs. Only then move to the next bolt. Done this way you can do in any order you choose.

 

 

Warm the engine up to operating temperature and set the valve lash to 0.012" on all. A tight valve might do this. Cost's nothing for parts too.

 

A cracked distributor cap, bad insulation on the plug wires, carbon tracking on the cap rotor or the coil tower might also cause a back fire. Check and clean plugs while you are at it they must be NGK BPR6ES intake and BPR5SE exhaust side. See if any old plug is different looking than the others.

 

 

At some time do a compression test. If one cylinder is down an exhaust valve may be burned or if two adjacent cylinders are low the gasket might be blown between them.

 

 

Get that head re-torqued ASAP because if it hasn't blown it WILL blow and it's over due.

I would set the timing to 3 degrees for now till this is sorted then you can experiment.

Thanks. I'll answer in order.

 

It does not blow any smoke out the exhaust, and I just retorqued the head before installing the engine. Loosened one bolt at a time in order and torqued to spec. Engine was completely rebuilt by previous owner around 5000 miles ago (with paperwork).

 

Valve adjustments already completed.

 

I'm currently using good NGK plug wires, brand new BPR6ES and BPR5SE plugs, and new OEM cap and rotor.

 

Compression test probably wouldn't be a bad idea.

[baseballguru44]

2 hours ago, NC85ST said:

Almost sounds like timing. You might want to check that it’s set correctly. Quick check would be to have someone try cranking it while you adjust the distributor one way then the other. If you can get it to spin easier, then you know it’s the timing. Sounds like the timing is retarded to much.

Thanks. This is the most common answer I've received. It doesn't seem to make a noticeable improvement. We started at 1 degree or so and went a degree or two all the way up to 10 degrees. It seemed to run best around 5 degrees.

[baseballguru44]

30 minutes ago, Charlie69 said:

Back firing through carb is usually timing.  Did you install new cap, rotor, plugs, and wires?

New OEM cap and rotor, new NGK plugs, good NGK wires.

[datzenmike]

Check the accelerator pump discharge. When stepping on the gas you should see a strong squirt of gas into the primary. 

 

Does it backfire when the choke is on?????

[Charlie69]

Please check to besure that the spark plug wires are correct.  Also that the coil wires are not crossed.   My Z20 and Z24 does not run as well if I cross up the Intake and exhaust coil wires.   Be sure that the rotor is lined up and actually firing on #1.  It is easy to get the distributor in wrong and then wire from the wrong position instead of resetting the distributor correctly.  I am guilty of doing this myself.

Edited January 13, 2021 by Charlie69

[datzenmike]

 

Never hurts to check. If one is wrong there will be at least two wrong. There is a feature that turns off the exhaust side plugs under heavy load so while both coils are the same and fire together, if switched and the intake turn off instead, it may run differently.

[Stoffregen Motorsports]

On 1/12/2021 at 9:01 PM, baseballguru44 said:

New OEM cap and rotor, new NGK plugs, good NGK wires.

This is the biggest red flag.

 

I know you said that the wires are in their correct locations, but replacing them leaves the possibility that they were not replaced in the correct order.

 

The problem does indeed sound like timing or firing order, so double and triple check the firing order before you go any further. Wouldn't hurt to check the TDC pointer to see if it got bent or something else caused it to be off it's mark.

 

Also, these sort of problems always come after work has been done. What else did you do before this problem started?

[baseballguru44]

Sorry for the delayed response. Over the past several days, we had been experimenting again and here are the results.

 

The distributor / wires were correct. I looked over them countless times. Again, it was only an issue at idle so I never seriously considered it. 

 

We decided to swap back the OEM Hitachi carb. Once swapped, it ran great for several minutes with no problems. Once the engine warmed up, however, it began backfiring and dying the same as with the Weber, which led us to think the valves. We popped the valve cover off and adjusted them again. Immediately, we noticed several were too tight. Once finished, we went and drove it with next to no problems. A great sign!

 

But, like always, it didn't end there. We were still having problems starting it, but it was inconsistent. Just for the heck of it, we drained my gas tank. It was foul smelling and had turned an orange tint. Immediately put in new ethanol free gas and it got even better. We drove it for a long time with no true problems. Once home, we decided to check the timing again. It was around 5 degrees last time we had checked, but was now around 15 degrees. We adjusted it down to 3 degrees and it ran poorly. Couldn't even back out of the driveway. We put it back to around 11-12 degrees, and haven't had any problems so far. I'm going to drive it over the next few days and post any updates / new issues.

 

Hopefully, if we can get this starting problem sorted out, I can put the Weber back on.

[datzenmike]

Here's the thing. Dual plugs means two ignition points in the combustion chamber. This is turn shortens how long it takes to burn all the fuel and air. With such a short burn time you must 'light the fire' later and much closer to TDC so that the expanding hot gasses can efficiently push down on the piston. Usually about 17degrees after TDC.

 

If one side set of plugs are not firing the burn time is longer and you have to advance the spark timing so you get that sweet spot at 17 degrees after TDC. Typically 12 degrees would fix this. You said the valve lash setting was completed.... so maybe the exhaust side coil isn't firing either.

 

Two things will cause this.

 

1/ the first fuse on the far left side of the fuse box is blown. It's a dedicated 10amp fuse that powers the exhaust coil

 

2/ there is a built in system that shuts off the exhaust side coil under load. It may have some problem and it remains off. Look at the wire harness to the distributor. There should be three wires taped in it's own harness and a forth white or light gray wire with it's own connector. Unplug and the distributor should fire all coils all the time.

[Charlie69]

How long did  this truck sit without being driven?  This information would have been helpful  in the first post.

Run some sea foam through the gas tank to help clean up anything left from the bad gas.

What carb are you running now. 

If you are running the stock electric pump and stock steel "Y" fuel line with the return lin hooked up, there is no need for a pressure regulator.

Pull your dip stick and smell the oil on it.  If it has a gas smell to it change your oil.

As Mike is explaing something is still not correct because of how you have the timing set.  Who put the rebuilt engine together.  The "Z" engines and the "L" engines when setting the timing chain up time to the #2 spot on the cam sprocket.  I had to reset my L20B when I got it back from the engine rebuilder because it was timed to the #1 spot.  The rebuilt Z20 I got out of the junk yard was also set to #1.

[baseballguru44]

16 hours ago, datzenmike said:

Here's the thing. Dual plugs means two ignition points in the combustion chamber. This is turn shortens how long it takes to burn all the fuel and air. With such a short burn time you must 'light the fire' later and much closer to TDC so that the expanding hot gasses can efficiently push down on the piston. Usually about 17degrees after TDC.

 

If one side set of plugs are not firing the burn time is longer and you have to advance the spark timing so you get that sweet spot at 17 degrees after TDC. Typically 12 degrees would fix this. You said the valve lash setting was completed.... so maybe the exhaust side coil isn't firing either.

 

Two things will cause this.

 

1/ the first fuse on the far left side of the fuse box is blown. It's a dedicated 10amp fuse that powers the exhaust coil

 

2/ there is a built in system that shuts off the exhaust side coil under load. It may have some problem and it remains off. Look at the wire harness to the distributor. There should be three wires taped in it's own harness and a forth white or light gray wire with it's own connector. Unplug and the distributor should fire all coils all the time.

Thanks for the info! I'll check it out.

[baseballguru44]

32 minutes ago, Charlie69 said:

How long did  this truck sit without being driven?  This information would have been helpful  in the first post.

Run some sea foam through the gas tank to help clean up anything left from the bad gas.

What carb are you running now. 

If you are running the stock electric pump and stock steel "Y" fuel line with the return lin hooked up, there is no need for a pressure regulator.

Pull your dip stick and smell the oil on it.  If it has a gas smell to it change your oil.

As Mike is explaing something is still not correct because of how you have the timing set.  Who put the rebuilt engine together.  The "Z" engines and the "L" engines when setting the timing chain up time to the #2 spot on the cam sprocket.  I had to reset my L20B when I got it back from the engine rebuilder because it was timed to the #1 spot.  The rebuilt Z20 I got out of the junk yard was also set to #1.

It sat for six months. I had a hard time finding an engine replacement after my Z24 block cracked. The long block was rebuilt by the previous owner, but I did everything else. Manifolds, timing kit, etc.

 

I did put some additive in the tank. Not a bad idea.

 

I only added the regulator originally because it seemed like a problem with the Weber, but obviously was unrelated. I will not be adding it back on. I currently am running the Hitachi with no regulator, but if I can get it 100%, I'd like to put the Weber back on.

 

Timing was properly set on the #2 mark on the cam sprocket. 

[datzenmike]

There's cam timing and there's ignition timing and in no way are they inter connected. #2 hole is a starting point, where the factory set it and will get you going. The actual check is to set TDC and look to be sure. If there is wear on the sprockets and chain or if the head was milled to flatten it the cam timing may need adjusting to the #3 hole. Again only way to know is to look at it.

 

Ignition timing has 3 components. There's the initial timing, set with a timing light, there's vacuum advance above idle and totally related to engine load and there's mechanical advance which is RPM dependent and also above idle. Mechanical and vacuum advance should not exist at idle but if your idle is too high they may be present and this makes setting the initial advance a waste of time.

[baseballguru44]

19 hours ago, datzenmike said:

Here's the thing. Dual plugs means two ignition points in the combustion chamber. This is turn shortens how long it takes to burn all the fuel and air. With such a short burn time you must 'light the fire' later and much closer to TDC so that the expanding hot gasses can efficiently push down on the piston. Usually about 17degrees after TDC.

 

If one side set of plugs are not firing the burn time is longer and you have to advance the spark timing so you get that sweet spot at 17 degrees after TDC. Typically 12 degrees would fix this. You said the valve lash setting was completed.... so maybe the exhaust side coil isn't firing either.

 

Two things will cause this.

 

1/ the first fuse on the far left side of the fuse box is blown. It's a dedicated 10amp fuse that powers the exhaust coil

 

2/ there is a built in system that shuts off the exhaust side coil under load. It may have some problem and it remains off. Look at the wire harness to the distributor. There should be three wires taped in it's own harness and a forth white or light gray wire with it's own connector. Unplug and the distributor should fire all coils all the time.

I went out and messed with it earlier. It is cold outside right now, so vapor smoke is obviously normal, but on cold start it starts very rough. Quite a bit of smoke as well. Blue tinted, not white. Until normal operating temperature is reached, any normal amount of gas will kill it and make restarting very hard. I made a video to show.

 

 

Once fully warmed up, the issues go away. I checked the fuse, it was good. Are you referring to the main distributor connector? Has red, black, blue, and red wire? Or the singular connector next to the vacuum advance? 

 

 

[datzenmike]

Either the timing is too advanced (15 degrees?) and fighting the starter or the battery is failing. Those pauses when starting are not right. Easiest thing is jumper from a vehicle with a good battery. If the turning power of the starter is improved then battery.

 

Fuse looks good or you tested both sides with a test lamp? Cannot be left to doubt or we'll spend 2 pages messing around to come back an find it was bad after all.

 

Next is check positive terminals on both coils with the ignition on. Should be 12v.

 

Next pull one intake and one exhaust plug wire and put a spare plug in the end. Lay on a grounded surface and turn the engine with the starter... got spark???

[baseballguru44]

8 hours ago, datzenmike said:

Either the timing is too advanced (15 degrees?) and fighting the starter or the battery is failing. Those pauses when starting are not right. Easiest thing is jumper from a vehicle with a good battery. If the turning power of the starter is improved then battery.

 

Fuse looks good or you tested both sides with a test lamp? Cannot be left to doubt or we'll spend 2 pages messing around to come back an find it was bad after all.

 

Next is check positive terminals on both coils with the ignition on. Should be 12v.

 

Next pull one intake and one exhaust plug wire and put a spare plug in the end. Lay on a grounded surface and turn the engine with the starter... got spark???

A new starter is installed and I have a spare battery. I also ordered some new NGK coils to be 100%. I will go through all of this and update in the next week or so. Thanks!

[Charlie69]

The Nissan factory coils rarely go bad.  I hate to see people through money into parts that are not bad. 

 

When the engine was put together before installation did you put a socket on the crank bolt and spin the assembly around several times?  Were there any tight spots during turning?  I ask because the Z20 remanufactured engine I purchased from the wrecking yard had tight spot during turning.  What we found through disassembly was 3 pistons and rods were in the wrong holes and one rod cap was on backwards.  After correcting these issues the engine now spins without tight spots.

 

Just as a precaution when I get an engine re built I tear it down before installation and check all clearances and that the engine is assembled correctly.  It is hard to find a shop that does quality work these days.

Edited January 17, 2021 by Charlie69

[Stoffregen Motorsports]

I detest rebuilt engines. There are only two shops in NorCal that I trust with engine building, other than myself.

[baseballguru44]

I received the ignition coils in the mail. Once installed, it still was having a hard time starting. Missing out very bad.

 

We found that with either coil running to the intake side coil on the distributor cap would cause it to "lock" while starting. But, if either coil was run to ONLY the exhaust side coil on the cap it would start and run perfect every time.

 

We pulled off the cap and noticed that there had been little to no wear on the intake coil contact on the cap and rotor, while the exhaust contact had normal wear. Despite it being a brand new OEM cap and rotor, I ordered and installed some others. After messing with it for several hours, we now have both intake and exhaust coils hooked up, and it runs and drives fine. Cold starts are still a bit rough, but not awful. Again, once warmed up, it runs and drives fine. No backfiring, no stalling.

 

The choke is working properly on my carb, so what could still be causing troublesome cold starts?

[Stoffregen Motorsports]

Chokes can be adjusted. And some jetting may be required too. Pilot jets are for idle mixture, but they can also affect cold start.

 

Start with the choke adjustment.