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Old 04-13-2004, 07:38 PM   #57
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Quote:
Originally Posted by smily
Is the O2 sensor you reference on the TBI?
I am under impression there are more than one O2 sensors in the system.

Smily
1990 should have two, one for each bank of the engine. It should be located just after the manifolds, and before the catalytic converter, if equipped.
Terry
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Old 04-13-2004, 08:32 PM   #58
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Quote:
Originally Posted by smily
Is the O2 sensor you reference on the TBI?
I am under impression there are more than one O2 sensors in the system.

Smily
There may be.

My 88 it is a single but I do know that there was a change in the FI in 90 on Suburbans and it would make sense that a second O2 be added for ODBI at that time. Some of it depends on the intake if it's needed. My 88 is a dual plane instake So even though the TBI is a 2bbl every other cylinder on each bank alternates sides of the TBI it is being fed. It should read the same from one bank to another in a perfect world. The Second was some of the OBDI standard to make a check that both sides read the same. O2 3 and 4 came in as a double check (and serious overkill) ont OBDII standards.
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Old 04-20-2004, 02:59 AM   #59
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Wink Cant climb hills

Something you should look at, the spade push-on connecter at the oil pressure sensor wil get loose (high heat causes loss of spring pressure and scale build-up). The resulting voltage drop slows the electric fuel pump when you need it most, i.e. , climbing hills. If it feels loose, replace it. Do not hard wire around the oil pressure sensor as this will stall the engine for lack of fuel if the oil pump fails.

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Old 04-20-2004, 04:15 PM   #60
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Quote:
Originally Posted by 59toaster
There may be.

The Second was some of the OBDI standard to make a check that both sides read the same. O2 3 and 4 came in as a double check (and serious overkill) ont OBDII standards.
O2 sensor #3&4 are downstream sensors behind the catalytic converters to make sure they are functioning correctly (read you haven't removed them). If they see a problem, the check engine light will come on with a Catalyst efficiency code. There is a way around this, consisting of a kit with resistors to simulate the reduction in pollutants from the cats so the light won't go on.
Terry
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Old 04-25-2004, 10:21 AM   #61
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It's Alive!

Well I wanted to get back to this post for a while. I rebuilt the carb and re-installed yesterday. The differences are amazing. First of all I had to back out the idle screw about five full turns to get her to idle at 750 rpm. Secondly, the power off the line has completely changed. She's got a little hot rod in her now. Third, the secondaries now open all of the way - so that's what it's supposed to feel like merging onto the highyway! and lastly, she climbed the biggest hill around at 65 mph with half throttle and no problems.

There is still a little bobble in the midrange (30 - 45 mph) but I think this might be a bad EGR valve. In any case it's so slight that it's only something that I would notice.

So I'm planning a test run to Indy and back then I think she's ready for a big Florida trip in May. Finger's crossed.

Again - so many thanks for the the advice from members. Your posts and advice gave me the confidence to try this rebuild myself. I also cannot recommend the book "Rochester Carburetors" by Doug Roe enough. It was my step by step guide through what had previously been a very intimidating component on my powerpant.
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Old 04-25-2004, 10:26 AM   #62
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Timing Setting?

Stephen:

Where are you currently running the timing?

Do you anticipate a change now you have the Carb up to snuff?
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Old 04-25-2004, 10:29 AM   #63
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I set it at 4 BTDC right before I pulled the carb. I'll recheck it now. With so many things moving around after the rebuild it might have changed too! I'll let you know.
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Old 06-01-2004, 11:00 PM   #64
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More info

OK....so I was not completely out of the woods yet. We left for FL two Saturdays ago and everything seemed to be fine. Just about two hours into this eighteen hour trip the engine cut out. I pulled over to the emergency lane and the %$^% wire broke off that darn relay again (mounted on the alternator bracket). So I fixed it (again) and we were off.

We got into the hills between Nashville and Chattanooga. At first everything seemed OK but then she began to hesitate at the top of hills. This progressed to the point where we decided to park for the night and continue the trip in daylight rather than chance a late night breakdown lane adventure (new house rule after the PA breakdowns).

On Sunday we continued to Atlanta but she was hesitating badly even on level ground. The feeling was different than before. The only way I can describe the difference is to say that this felt like it lost power whereas before (in PA) it felt like it was always under powered but would gain power intermittently on hills. Same result however - not enough power.

This time it really felt like fuel starvation. Prior to this trip I had replaced the the entire ignition, rebuilt the carb and fixed the choke heater. It had to be fuel delivery - right? I was set to meet up with 59toaster in Atlanta and we ended up taking an auto parts tour of Atlanta to find all three fuel filters I needed. (See 59toaster rocks). I installed all three filters and viola - power again - but for how long?

I should also point out that my mileage was still terrible on the trip down.

We made it to FL, had a great week and headed for home on Saturday morning. We made it about 150 miles on the FL turnpike and the tach started jumping up to 7000 rpm and the voltmeter would bottom out. The dash lights would dim and she would sputter all at the same time. I pulled into a rest area and she stalled. I figured "That %$^& wire". But nothing was wrong there. At this point she would not even turn over. I threw a test light on the relay and no power. Hmmmm. So I started taking off wire looms and tracing power...about an hour later I found the problem. The 12V feed side of this relay (which also feeds the ignition side) runs down the front of engine, along the oil pan and connects to the starter relay. Well....this and one of the battery cables were touching the number eight header primary and burned to a crisp. The 12V feed has broken completely and I saw lot of arching evidence on the header itself. So two more hours on my back and I was able to rig up a new wire, taped everything with two rolls of electrical tape, loomed it up out of the way of the header and everything worked the entire way home.

I have to say at this point that the FL travel plazas are excellent and had enough food and shopping to keep my wife and our three kids [relatively] happy for three hours while Dad worked on the RV again. More like malls in the median than the rest stops I grew up with. I highly recommend breaking down in one

Interestingly, I saw a significant improvement in pulling power on hills and I think my mileage got better as well. (Not exactly sure n the mileage as I ran her into Louisville pretty empty so I can drop the fuel tank for a cleaning and sealing - but I got another 75 - 100 miles before hitting half full on the gauge than on the way down)

This one was my fault. I replaced the started on a cold night in a parking lot when the engine still had factory manifolds on it. I put the headers on right before the PA/CT trip. I did not go back and check the wiring to make sure it was clear of the headers. I'm pretty sure I've been burning that wire and grounding it to the header since then.

So this weekend's projects now include replacing all of those wires properly with 8 gauge wire, building a box to remount the %$^& switch and if I get ambitious - drop the tank and take it up to the dealership for a cleaning and inspection.
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Old 06-01-2004, 11:14 PM   #65
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Electric Choke?

Wire shorting out caused not enough voltage/ amperage to the choke heater so you were driving with a partly closed choke on the way down. With it fixed on the way up the choke was fully open hense the better MPG.

Other possiblility is stale or this new gas we have been seeing. THis new low polution summer mix SUCKS! all my vehicles sudenly have developed hard start issues when cold. Honda by far has been the worse but I'm still chasing PO and his stupid mechanic issues on that car. It had a VERY loose timing belt and they never checked it. Wouldn't pass emmissions as a result so the $600 Fix has really made a mess of things. Got it making 31mpg now but still has issues.
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Old 06-01-2004, 11:32 PM   #66
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Yeah...I had this on a trip to St Louis when the choke heater wire broke. Partially closed choke loaded up the plugs so badly it barely ran at idle. I had to replace all of the plugs.

I also had that strange missing on multiple cylinders when I put a timing light on them. I could never figure out what this was and ended up replacing the entire ignition system chasing it. I suspect that this wire was causing the coil to loose power completely or at least seeing a dropped voltage which would also add to my drop in fuel economy.

31 mpg....thats hard to think about when all I want to do is see 9 mpg
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Old 06-02-2004, 12:21 AM   #67
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$1000 Bomb honda's rule! Parking the burb and driving this saves us at least $200 a month. Actually Chili drives the burb now but a tank last a month with here not the week it lasts with me. Probably saves a Min $250 a month now that we are pushing $2 a gallon here. That car paid for itself in a little over 3 months. Might just have to fix tha A/C though.
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Old 06-02-2004, 07:44 AM   #68
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Quote:
Originally Posted by swebster@myrvadvanta
OK....so I was not completely out of the woods yet....This time it really felt like fuel starvation. Prior to this trip I had replaced the the entire ignition, rebuilt the carb and fixed the choke heater....I should also point out that my mileage was still terrible on the trip down....
I ran her into Louisville pretty empty so I can drop the fuel tank for a cleaning and sealing - but I got another 75 - 100 miles before hitting half full on the gauge than on the way down)...
So this weekend's projects now include replacing all of those wires properly with 8 gauge wire, building a box to remount the %$^& switch and if I get ambitious - drop the tank and take it up to the dealership for a cleaning and inspection.

Steven:

My gas gauge is becoming more and more erratic. It indicated almost a half a tank when I pulled into a recent fuel stop, and it took over 60 gallons to fill....do the math. You have enough hours in other aluminum conveyance mediums to know to not trust a gas gauge. I go strictly by the mileage divided by my worst (best) guess of the gas mileage (5 mpg), so 80 gal X 5 mpg = 400 miles maximum travel distance prior to fill up. Usually a lot more frequent.


Changing lanes entirely here and addressing your rebuilt carb. When I rebuilt the carb (or tried to) on the Onan, both of the needle jets were really worn. I blamed the wear on air being sucked in with the fuel, but now wonder if it was not a case of a combination of solids pollutants aggravated by erosional velocities caused by the possibility of air entering the gas system side of the carb. Since the genny does not get the multiple filters that the 454 carb does, the Onan might be eating a bunch of tank solids the main engine carb is not (?) being exposed to. What shape were your main carb needles in when you rebuilt the 4 bbl?

Just wondering, 'cause, as far as I know, my carb has never been broken into.

I'm still raising a lot more questions than I'm answering with the 345. The famous Onan "Mysterious Stall" has reappeared.......that's a top priority to fix before taking ANY warm weather trips. Still think the problems are fuel related. I plan to install a Racor fuel filter separator upstream of the existing main engine engine electric pump, and run a new fuel line from there to the Onan. Probably will move the Onan fuel pump to the new filter location. PeterH-79MH would probably recommend at this point to trash the Onan and replace with a water cooled Honda. He may well be right.
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Old 06-02-2004, 08:01 AM   #69
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Quote:
Originally Posted by 87MH
My gas gauge is becoming more and more erratic. It indicated almost a half a tank when I pulled into a recent fuel stop, and it took over 60 gallons to fill....
I remember reading/hearing on the radio the other day that the Shell gasoline company was recalling a lot of gasoline (in the Florida area?) due to high sulphur content. Seems the sulphur was ruining the fuel gauge sending units in new cars.

Don't know if it applies to this situation, but thought I would pass it on.

Tom
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Old 06-02-2004, 08:43 AM   #70
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Dennis - my gauge is also not very reliable lately Last year it was pretty well dead on in 20 gallon increments but on this recent trip I topped it up when it was between 1/4 and 1/2 and it took 70 gallons! That could have been bad.

So now I fill at the half mark and it's taking about 50 gallons. Stil not right but leaving me a 30 gallon reserve. This is one more reason I'm considering dropping the tank.

The needles on the QJet were in great shape. I checked them for both mechanical damage (bent, chipped, etc.) and wear damage using a big magnifying glass and could not find anything visibly wrong. Of course they are behind three filters and based on this FL experience the filters seem to be doing their job.

I plan to install an additional inline filter to the genny just to be sure. The little Onan screen has never made me feel very good about protecting a $4000 generator! I think Peter told me once that the only replacement part number you'll even need for the Onan is H-O-N-D-A

Tom - we had the same gas issue here in KY but it seemed to affect only combination fuel pump/sending units in the tank. Not sure what it does to our older style sending units but I certainly saw a big difference in accuracy on this last trip
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