1979 DATSUN Sunrader "will the 6bolt foollies kill me?"

[RyanG]

Hey there,

looking for someone who is familiar with the Datsun 620 Sunrader Motorhome.

I just picked it up, it's 1979 620, with a L20B 4 speed manual.

 

Rear axle is 6 bolt, but not a FF  and the rim is this weird one piece with two tires on it. Is this just as dangerous as the early Toyotas, or did Datsun make their rear axles a little stronger?

 

If I need a 1 ton dually rear axle, what are my options for a rear axle swap?

 

Iv'e also got some engine issues and from reading a bunch of posts I'm assuming it's related to the vacuum system or the electric choke, but I'll list them just incase someone has a different idea. 

Have some serious Idling issues, starts up just fine, revs high, I depress the gas and it loweres RPM then dies. It won't stay running unless I feather the throttle. Its also missing and backfiring a fair bit.

The Air pump has been disconnected and there are quite a few hoses not hooked up.

Would love to pic someones brain who owns one of these neat motorhomes.

Thanks so much

 

Here are some pics of the rig

 

https://postimg.cc/zHSCN5nN

 

https://postimg.cc/fShc1kS5

 

https://postimg.cc/34GjL2Nd

Edited August 23, 2020 by RyanG
Added photos

[datzenmike]

 Why would you be thinking of replacing the rear axle?????? Are you having any problems with it?

 

Fast idle when engine cold is normal. Steping on the gas will release the choke if the engine has warmed and the fast idle will drop off. Releasing it too soon when it is still too cold for proper running can result in a poor idle and driving. Backfiring can be from the mixture too lean and this is why the choke should be on. The choke may just need to be adjusted so it is running richer.

 

When it is warmed up does it backfire through the carburetor? That would be something else.

 

 

There's a white one in Courtenay but '77 or older.

[RyanG]

Thanks for the reply datzenmike.

 

" Why would you be thinking of replacing the rear axle?????? Are you having any problems with it?"

 

Ive done a bunch of reading on the Toyota Motorhome forums and the non Full Floating dually Axles that Toyota made were recalled due to failure. But this Datsun has been running like this for 41 years, so maybe you're right, why change it out. 

 

I drove the motorhome home, about 35km and it never stopped stalling anytime I would take my foot off the gas. It just doesn't want to idle. Should I try and mess with the idle screw, or is it more likely to be a dirty carb and start cleaning? The engine run wells when the choke is engaged, 

 

The engine would miss now and again during driving, but could could be many things. 

 backfiring was happening mostly when I was gearing down.

 

I appreciate any and all tips, thanks.

 

Ryan

 

 

[]2eDeYe]

Does it have the factory carb?

[datzenmike]

Good Steve.

 

 

3 hours ago, RyanG said:

Thanks for the reply datzenmike.

 

" Why would you be thinking of replacing the rear axle?????? Are you having any problems with it?"

 

Ive done a bunch of reading on the Toyota Motorhome forums and the non Full Floating dually Axles that Toyota made were recalled due to failure. But this Datsun has been running like this for 41 years, so maybe you're right, why change it out. 

 

I drove the motorhome home, about 35km and it never stopped stalling anytime I would take my foot off the gas. It just doesn't want to idle. Should I try and mess with the idle screw, or is it more likely to be a dirty carb and start cleaning? The engine run wells when the choke is engaged, 

 

The engine would miss now and again during driving, but could could be many things. 

 backfiring was happening mostly when I was gearing down.

 

I appreciate any and all tips, thanks.

 

Ryan

 

 

 

Don't fix what isn't broken.

 

 Listen near the rear of the carburetor and have someone turn the ignition on off on off on off. (but not try to start) What you should hear is a sod

ft clicking sound. Does it???? This is the idle cut solenoid and it had to be working for gas to enter the idle circuit inside the carburetor. Without it... no idle.

 

Some slight backfiring out the exhaust is normal on all carbed engines when decelerating. This can be lessened but later

[RyanG]

3 hours ago, ]2eDeYe said:

Does it have the factory carb?

Yes, I believe it is.

 

2 hours ago, datzenmike said:

Good Steve.

 

 

 

Don't fix what isn't broken.

 

 Listen near the rear of the carburetor and have someone turn the ignition on off on off on off. (but not try to start) What you should hear is a sod

ft clicking sound. Does it???? This is the idle cut solenoid and it had to be working for gas to enter the idle circuit inside the carburetor. Without it... no idle.

 

Some slight backfiring out the exhaust is normal on all carbed engines when decelerating. This can be lessened but later

 

I couldn't hear the solenoid clicking. By any chance is that Anti-Diesel solenoid powered by a round fuse in the cab labelled Solenoid? 

Sorry, I guess I should be moving this chat to 620 L20B engine forum.

 

 

[datzenmike]

It may be. Never trust a glass fuse by just looking at it. Test it or replace it. You should have a $4 test lamp. With ignition on lamp should light on both sides of the fuse.

[]2eDeYe]

You can test the wire at the solenoid for power as well

[RyanG]

Well we're making progress!

I replaced the fuse and got the power to the solenoid, now it idles really well but too high. Tried screwing in the idler screw almost all the way , but still idling quite fast. 

 

Also replaced sparkplugs, adjusted timing (just centred the mark) and sprayed carb cleaner into the carb inlets. 

 

She's running quite well just a little fast. 

 

 

 

 

[wayno]

He likely has a stock looking H190 axle but they are possibly different, there is a round raised area on the top of the housing where the dropout is, he also has a set of them weird rims that are one piece but 2 tires mount on them, if you look at the rims in the photos he posted you will see it has a really deep rim, I have seen a couple 620 motor homes with them over the years.

I have heard that regular tire places will not touch them rims.

I have a couple Nissan C200 dually axles/rims if your interested, but I live in Vancouver WA, I expect they would bolt right in, but Vancouver Island is quite a ways away.

The C200 axle is around 76" wide from outside of tire to outside of tire, probably around 74"/75" from the outside of the rim lips, they are 4.37 geared axles.

I also have dually adapters from a 1979 Datsun 620 I believe, they use stock Datsun rims but they are old school.

 

[datzenmike]

7 hours ago, RyanG said:

Well we're making progress!

I replaced the fuse and got the power to the solenoid, now it idles really well but too high. Tried screwing in the idler screw almost all the way , but still idling quite fast. 

 

Also replaced sparkplugs, adjusted timing (just centred the mark) and sprayed carb cleaner into the carb inlets. 

 

She's running quite well just a little fast. 

 

 

 

 

 

Fast idle cam on the choke linkage may be stuck. WD-40 the back of the carburetor and move all the linkages including the choke flap while holding throttle 1/2 open to release the interlock.

 

The white plastic thing top center...

 

[RyanG]

Wayno, I'm very interested in the Dually Axle, I'll do some research on it. And we will have to wait for that border to open up. 

 

I'm going to post a couple pictures of my Carburetor, I'm either missing the fast idle linkage or its not the stock carb. 

 

 

[datzenmike]

I can see the fast idle cam, it's metal on yours. Spray with WD-40 and move everything to loosen it up.

 

Fast idle adjustment screw is maybe hidden in that picture. Behind the idle cut solenoid with the red wire.

 

.
 

[RyanG]

You're absolutely right, loosened it up and found the fast idle screw hidden in there. Just trying to find the right balance now. It's miles better, but still firing a little rough. Thanks so much! 

[datzenmike]

The screw that is more to the front of the carb is the idle mixture screw. This sets the air to fuel ratio, here's how to adjust it....

 

Thoroughly warm the engine. Choke must be off. Idle must be below 1,000, lower is better. For best results the timing should be set/checked 12⁰ BTDC and the valve lash confirmed 0.010" intake and 0.012" exhaust with the engine HOT. You could set the idle mix to get the engine to run so you can set the timing and valve lash but it should be checked after.

 .

 

Turn idle as low as it will run.This will make any changes easier to detect.

Turn the mixture screw in or out until the idle drops off and is worse. Use 1/4 turns with a pause for it to take effect.

There is up to one full turn where it will idle very well with it dropping off on either side. Set roughly in the middle of this zone.

You are looking for the strongest, fastest, smooth idle.

Presumably the idle strengthened and went up, so turn it back down and repeat the in and out adjustment and setting in the middle and turning the idle back down.

Keep going, you may have to do this 7-8 times.

When you have the strongest, smooth idle and the RPMs are 750-850 you're done.

 

[RyanG]

13 minutes ago, datzenmike said:

The screw that is more to the front of the carb is the idle mixture screw. This sets the air to fuel ratio, here's how to adjust it....

 

Thoroughly warm the engine. Choke must be off. Idle must be below 1,000, lower is better. For best results the timing should be set/checked 12⁰ BTDC and the valve lash confirmed 0.010" intake and 0.012" exhaust with the engine HOT. You could set the idle mix to get the engine to run so you can set the timing and valve lash but it should be checked after.

 .

 

Turn idle as low as it will run.This will make any changes easier to detect.

Turn the mixture screw in or out until the idle drops off and is worse. Use 1/4 turns with a pause for it to take effect.

There is up to one full turn where it will idle very well with it dropping off on either side. Set roughly in the middle of this zone.

You are looking for the strongest, fastest, smooth idle.

Presumably the idle strengthened and went up, so turn it back down and repeat the in and out adjustment and setting in the middle and turning the idle back down.

Keep going, you may have to do this 7-8 times.

When you have the strongest, smooth idle and the RPMs are 750-850 you're done.

 

 

 

" set/checked 12⁰ BTDC and the valve lash confirmed 0.010" intake and 0.012"

Sorry Datzenmike, this part is a little foreign to me, should the engine be timed to 12 degree BTDC? I'm not familiar how to check valve lash or intake.

 

Thanks a ton for the carb adjustment advice, that all makes sense. 

 

[datzenmike]

 

You need a timing light and the timing scale is below the alternator next to the crank shaft pulley. It's marked in 5⁰ increments. The pulley will have a notch on it. You'll be able to see the notch in the timing light flash. Adjust by slightly loosening the distributor and turning it.

 

 

 

 

 

[RyanG]

Gotchya! And thanks for the photo as a reference, very hard to read the degrees on my timing scale. 

[datzenmike]

Between a peak and a valley is 2.5 degrees,  5 degrees between peaks.

[RyanG]

Tried to get the timing and idle adjusted and  when I tried to start the truck wouldn't idle after warmed up. Checked the fuse labelled solenoid and it was burnt. Guessing the idle solenoid pulled too much or shorted?  I had the proper rated fuse in there 10 amp, but an old one.

 

Going to replace and see where we are at, just wondering if you have any idea what would cause it to short out. 

[RyanG]

That fuse labelled solenoid powers the relays under the hood as well, so who know what caused it to short. Changed it out and we're back in business.

 

Amazing advice Datzenmike!! Timing is bang on now and she's purring like a kitten!!! Just fantastic. 

 

 

[Tonyniebrugge]

Do you have interior pics of this Sunrader? I’m looking to purchase a shell of this model and it has been completely gutted. Wanting to see what the layout looked like.

 Thank you for your time