Very specific Hitatchi carb problem.

[grasscutter96]

Specs: 1984 GL 4x4 4sp wagon. 67,230 miles. Car died while driving it around town. Recently purchased car, after selling my 2001 Legacy. Car sat since 1991, hence the low miles.

 

Been driving it for about 2 weeks with no problems.

 

What I've done so far.

 

1- replaced filters (both).

2- checked fuel pump operation- amount & pressure ok.

3- pulled tank. Cleaned tank (was in very good shape), blew out and checked all tank connections, hoses, etc. All ok.

4- Did a 'quicky' rebuild of carb. (Clean out float bowl, blow cleaner through

the passages, new gaskets)

5- Car now starts, but stalls / dies unless I hold throttle to 1500rpm+

6- Rebuilt carb again. This time took A LOT of time to inspect, clean.

Found numerous jets plugged, stripped.. the whole thing was a mess! Did a Complete dis-assemble, soak, etc. All new o-rings, gaskets, needle/seat, checked float level, did it all!

7- Car starts, but same problem. No idle unless i increase idle screw to set idle @ 1500rpm+.

8-Took car for a drive. As long as I keep the rpms above 1500, it will drive and accelerate great!

9- Compression test. 150-155 on all 4.

10- Checked all vac hoses. With only 67K on vehicle, all the rubber is in great shape, soft and no cracks. No hoses missing.

11- checked timing. Right on.

12- checked choke operation. a-ok.

13- checked idle / air screw. makes no difference if its screwed in, out, etc. Still stalls out.

 

Here's my specific question. Since it will run when the rpms are increased, that signifies a problem with the idle circuit? Correct?

 

I'm going to pull the carb off and go through it one more time. Is there a specific area I should focus on? Is it possible I've got an internal fuel passage blocked? Any idea which one? Or am I missing something else?

 

I appreciate the assistance.

[Quidam]

Hey,

 

You could try taking out the idle mix screw and spray some carb cleaner in there and or compressed air. Just a thought, take the idle screw out and see what it does.

 

Doug

[GeneralDisorder]

Yes - remove the roll-pin that blocks access to the idle mixture needle if you haven't done so and remove it. The idle circuit is blocked it sounds like.

 

You can remove the throttle base and you should be able to get better access to the idle circuit fuel gallery, etc.

 

That's a long time to have a carb sit - chances are you just haven't got all the crap out of it yet. Boil the throttle base in a mixture of white vinegar and water.

 

GD

[ferox]

You can also get to the rest of the idle circuit by taking the choke body off. I presume you have a manual of some sort that shows some fuel circuit profiles. I had to use compressed air recently to unplug mine. Also make sure the anti-dieseling solenoid is working properly.

[MilesFox]

I had similar problems with mine, but would idle and not rev out. I claned out the carb by removing the top. I ended up doing intake gaskets. probably not your case.

 

anyway, after all that the car would drive, but not idle well. I turned up the idle to compensate, was rough. I ran some fuel treatment through and it cleared out after 80 miles, i was able to turn the ilde down.

 

I used a 23 dollar bottle of treatment that is designed for removing varnish and rejuvenating old gas. My car had sat for 2 years before i got it running. I used 2 oz to a full tank

[grasscutter96]

Sounds great. I'll try those tid bits of info. Can't hurt. Carb is coming off again this weekend. I'll give it another soaking!

[Gloyale]

Did you pull the Venturi horns and replace the tiny o-ring that seals them to the carb body? At idle, if the o-ring there leaks, there isn't enough venturi effect to pull through the idle circuit.

 

You have to grab the horn with pliers, and pull it up. Keep track of the roll pin that keeps it seated. Install the new o-ring, insert the horn in it's seat, and then reinsert the roll pin.

[grasscutter96]

YES! The idle circuit needs some more attention.

 

Today I did a bit more diagnosing...I can screw the idle mixture screw all the way in, no change! I can actually take the idle mix screw out of the carb, and there is no change!

 

When screw was out, I sprayed carb cleaner in that passage. Car smoothed out its idle for a brief few seconds, while it burned the carb cleaner. Right now, i turned the idle screw up, so the rpm is @ about 12-1500. @ this range the car will stay running and will not stall.

 

Quote from HTKYSA..."if you still can't change he RPM with the mixture screw, some passages in the carb are plugged. The carburetor needs rebuilt". Can't be stated any more plain than that!

 

Guess, I'm back to doing the full soak/blow/etc rebuild again! ARGH!!

 

**Side note: I do not hear any 'click' from the anti-diesel solenoid engage/disengage. Is that normal? With the key in 'on' position, I would plug and plug the 2 prong carb wiring harness connector (1984 feedback carb). No 'click' was ever heard. Could the ADV be bad? How do I check?

[Gloyale]

 

**Side note: I do not hear any 'click' from the anti-diesel solenoid engage/disengage. Is that normal? With the key in 'on' position, I would plug and plug the 2 prong carb wiring harness connector (1984 feedback carb). No 'click' was ever heard.

 

The power for the Anti-Diesel solenoid comes from the Fuel Pump Control Unit. No power is sent out to the Fuel pump, The choke, or the Anti-Diesel Sol. until an igniton pulse is detected (tach signal)

 

You won't hear any "click" just turnng the key on.

 

If you want to test the solenoid, just put 12v to it's wire directly and see if it clicks. FWIW, if the car runs fine, and shuts off fine(no dieseling)......then the ADS is working.

[grasscutter96]

Gloyale: yeah- good call on the small o-rings. I bet a lot of folks miss that. I actually missed it the 1st time I pulled the carb apart. Got them in now. But still no carb change.

 

Also: yes, the ADS (or ADV) is working.

 

What I think might be compounding my problem is: when I was tearing the carb apart, I was writing down the jet #'s so as to make sure the air bleeds, mains, secondary jets, etc. would be put back in same spot... well... the piece of paper I scribbled it all down on, is gone. I can't find it.

 

So, I used some judgement on jet selection. Small # main on primary, larger main on secondary. Etc. I very likely did not put things back as they should be.

 

I've not been able to find out where jets exactly should go. Went to dealer and they were nice enough to give me a photocopy of all the breakdown and parts list for the carb. I had them put in the VIN, to see if any specific carb info would come back. Nothing.

 

Anyone else have an idea what jets should go where?

['84 Flat-Four]

I can't answer that without referring to the FSM, so I thought I'd throw this your way (and anyone else of course). You can most likely match the spec sheet to the blow-up diagram sheet. I hope this will help you out a bit...

 

https://acrobat.com/#d=sr**gQbAR*HAAwgxL0zLgw

[naru]

Gloyale: yeah- good call on the small o-rings. I bet a lot of folks miss that. I actually missed it the 1st time I pulled the carb apart. Got them in now. But still no carb change.

 

Also: yes, the ADS (or ADV) is working.

 

What I think might be compounding my problem is: when I was tearing the carb apart, I was writing down the jet #'s so as to make sure the air bleeds, mains, secondary jets, etc. would be put back in same spot... well... the piece of paper I scribbled it all down on, is gone. I can't find it.

 

So, I used some judgement on jet selection. Small # main on primary, larger main on secondary. Etc. I very likely did not put things back as they should be.

 

I've not been able to find out where jets exactly should go. Went to dealer and they were nice enough to give me a photocopy of all the breakdown and parts list for the carb. I had them put in the VIN, to see if any specific carb info would come back. Nothing.

 

Anyone else have an idea what jets should go where?

 

 

Small main in the primary 111,114 calif.or 2wd

Small air bleed in the primary 70,60 if calif.or 2wd

Sec. are the larger ones left over

Slow air bleeds are reversed,larger in the primary-160 or 150

 

Idle mixture screw should work regardless of jet placement.Sounds like the idle passage is still plugged if the ADS is OK.Compressed air blown thru the idle mixture screw hole should come out in the throttle bore and inside the float bowl.(w/ADS powered up or removed)

 

Better yet,blow thru the ADS port w/it removed.

Edited January 28, 2010 by naru

[GeneralDisorder]

Jet sizes won't affect the idle circuit. When the throttle is closed enough for the idle to operate the mains aren't online anyway.

 

Hitachi idle jets are fixed - you can't easily change them - the only adjustment is the mixture screw.

 

GD

[naru]

Jet sizes won't affect the idle circuit. When the throttle is closed enough for the idle to operate the mains aren't online anyway.

 

Hitachi idle jets are fixed - you can't easily change them - the only adjustment is the mixture screw.

 

GD

 

Don`t know if you can swap them side to side,but,neither the slow air bleeds nor slow(idle) jets are "fixed".They are screwed in like the others.

Factory used at least a couple different slow bleed jets.

 

Here is a nearly identical Hitachi:

http://www.preterhuman.net/texts/automotive/Hitachi_Carb_DCH_DCP_DRJ340.pdf

[GeneralDisorder]

I must have them confused with that darn Q-Jet I've been working on

 

In any case there is not a secondary idle system present on most of the EA carbs (they are cast for them, but not actually present - no mixture screw, and vacant jet holes), and the idle jets aren't interchangeable with the mains so I doubt he's got them in the wrong place, etc. More likely all the passages weren't open to the cleaner when it was dipped. It's common for people not to strip carbs far enough to get them 100% clean inside.

 

GD

[coxy]

May be worth a try but Hitachi carbs are notorious for pluging the idle circuits on anything they are fitted to as they are so small.

One trick I have used on mazda and Nissan carbs with those symptoms was to reverse number 1 and 4 plug leads start the engine it will run like crap and backfire when you try to rev it,that is the secret the backfiring through the inlet manifold quite often will clear a blocked idle circuit,problem fixed without a carb rebuild.

When trying this you useually only have to run them like this for 30~60 seconds,if it doesn't work by then it won't in your case,probably also usefull tip for webers as many variants have an unfiltered idle air bleed jet on the outside of the carb and they often block up.