I could use some help diagnosing this issue...

Daily at 50+mph speed I notice a power gap/loss when I give the car more gas. It's a momentary drop in power before the car begins to accelerate. This pause occurs with a high pitch whine/sucking sound. As i apply more gas this passes and the car is fine.

Two days ago, the scenario repeated however I was driving in an unexpected thunderstorm. I had the same scenario but this time the car was sputtering and stalled at highway speed. I was able to get the car started but as soon as I gave it as to get going again it died. Eventually using 1/4 throttle was able to get the car started again. Next two days of driving no issues whatsoever and was not able to reproduce. No rain either though. Behavior is like i described above with slight hesitation.

This is my first carb car, so my wild guess is a vacuum leak and with the rain it was getting some moisture in? Ideas?

Thanks in advance!

 

Can you tell me what engine you have and weather its carb'd of SPI or MPI
If carb'd you may need to strip down carburettor and give it a good clean also the dashpot piston has the tendinsy to to wear out and need replacing.......

 

It is an 1982 998cc. I don't think it's spi.

 

Pop up a pic of engine in bay so I can take a look esp Engine NO:and carb..

 

Here you go.. Uploaded a couple pics

http://picasaweb.google.com/pbhathen...eat=directlink

 

Hi..I have had a few thoughts When was your engine last serviced??
was the timing done???
looking at the pics I think your carb needs an overhaule, and check the dash pot piston plunger for wear...........
and sometimes the valve tappets are to tight causing timming probs....

 

Not sure on the service history. I've had the car just a couple weeks at this point, and have been going through various issues as they arise.

From the title papers it seems like the previus owner drove it less than 500 miles in 2.5 years, so I think most maintenance was neglected.

Any write-ups on the dash pot and piston? My Haynes just mentions what type of oil to put in, nothing else. Thanks

 

this site may be of help.............

http://www.sw-em.com/su_carbs.htm

http://www.sucarb.co.uk/

 

Thanks. I was looking at rebuild kits for the HS4 Su carb, and it looks like I could get a remanufactured one from minimania for almost the same cost. any thoughts on just buying a rebuilt one from them, should I be looking to upgrade the carb or just a replacement... Sorry for the rookie questions

 

well a rebuilt carb should work... but if I were you I would give the engine a good service IE new points and condensor, oil filter, plugs, air filter, and ajust the tappets in the following order.
No:1 valve open ajust No:8.
No:2 open ajust No:7
No:3 open ajust No:6
No:4 open ajust No:5
No:5 open ajust No:4
No:6 open ajust No:3
No:7 open ajust No:2
No:8 open ajust No:1
and of course new oil.........
once done try out your mini and seeif this has made a differance............

 

previous post is excellent advice but I'm going to caution you to not follow it.

If you've been following my posts you may have seen I believe part of my problem was changing too many things at once. Now that the car won't run I'm having a hard time finding out what improvement wasn't . . .

attack these things one at a time . . . .

1. Haynes mentions what type of oil to put in the carb-pot..... is it full? I use 3-in-1 oil btw . . . if the oil in the pot is 'wrong' the carb won't deliver the fuel especially under load. The oil dampers movement of the needle which impacts fuel delivery.

2. You can do a lot to an SU carb to service it short of a rebuild. There are three screws around the pot cover. Remove those and you can pull the pot cover. Pull that and you can get to the piston spring and the needle. Pop the retaining ring at the top of the pot plunger tube and you can sep' the pot cover and the piston. If like mine, you'll find a ton of built up gunk in here. Clean up everything with standard carb cleaner. Want the name of a good reference book? PM me. An SU piston that is sticking will be unable to deliver fuel especailly under acceleration. Know where the lift button is to check for free movement?

3. You can buy a timing light at Harbor Freight for about $20 and never worry again if your timing is on or not. It ain't a great timing lite but it works and using it is EASY; a 5 minute job.

4. Pull the plugs - what do they look like? Plug color can tell you A LOT about how the car is running. You want to see dry plugs and a light tan color (biscuit). Gunked up? Replace 'em and find out why.

5. You recognize the importance of 'vacume integrity'. Hoses are cheap. Replace every vac' line you are not 110% sure of.

6. Coils are cheap ..... plug wires are cheap ..... points and condensors are cheap but replace THEM. Replace points with a Pertronix Ignitor and never worry about points replacement again.

If you would like a complete new 45D dizzy from Pertronix (electronic - with a 2 wire hook up) at $50 off list {$150 ur cost} PM me in the next 24 hours and I'll sell one I don't need but am about to return .... (personal penance for my sins to your potential gain)

 

Wow. Thanks to you both. Great info/advice. I've changed oil, filter, air filter, and just picked up plugs this weekend to replace.

I don't know if the dash pot is full, haven't checked yet. I'll do that. And changing the hoses is a simple one I should do too. I'll start there and keep going through the list step by step.

 

Thats good advice............But sort out the fault first before you go to the expense of electronic dizzy...........

 

I no longer have it to sell, but check the cost of

points, condensor, rotor and cap

versus

a replacement dizzy from Pertronix with the Ignitor installed . . . .

those little bits add up fast . . .

and doing it ONCE versus once a year for the next how many?

However I agree ..... I digress. Find your problem and fix that first. REMEMBER:

ALWAYS and I mean ALWAYS ensure the ignition is 110% b4 you futz with the fuel system. Do NOT adjust the carb until you know the electrics are 110% right . . .

 

Well I cleaned the dashpot, replaced the oil in it etc. Not nearly as much build up as I expected. It was actually pretty clean. I inspected the hoses and saw no visible tears etc. And still have to replace the plugs.

I took this video today. Car was warm, choke was in. Not the best audio/video, but in the middle of it you'll see me give it throttle and hear the engine kind of burple... This was happening to me on highway that day where it was on the edge of stalling while trying to give it gas. Also, on all of the accelerations there is a noticeable lag and stumble in rpm from the sound of it before the acceleration climbs back up. Is this normal behavior?

http://picasaweb.google.com/lh/photo..._AI?feat=email

 

Thats needle issues, the choke needs to be reset......wind in the to large brass nuts fully in under carb and then turn out 3 flats this should give you a good idle to start with then turn 1 flat at a time till flatspot goes..........

 

Not sure where the 2 nuts are that you are referring to... Are they visible in this pic http://media.photobucket.com/image/f...6/P1010100.jpg

 

still waiting for your Haynes?

Haynes has a generic proceedure for adjusting an SU .... problem is: adjusting an SU is adjusting for idle only .... I have a better book, but it does not have a better proceedure.

With an SU the fuel supply under acceleration is controlled by "the needle" and finding the right needle in the US is quite a hunt as NO garages are familiar with this set up. In UK they (MiniWorld) recommnend putting the car on a dyno, with a gas analyzer hooked up and with an SU expert there with a handfull of needles in hand . . .

So I'll come back to asking what your plugs look like. You want to replace 'em? GREAT! But their current condition can tell a lot. On the other hand your engine appears to be stock and therefore there's little reason to suspect your needle is wrong. For example, if you were to remove all the emmissions crap and the stock air filters and fit a "cone filter" aka a low resistance intake, you'd need a different needle.

Poor performance under load (acceleration) can come from two places.

1) the ignition system
2) the fuel system

You SHOULD eliminate ANY possible ignition problem b4 screwing with the fuel supply. You bought plugs? GOOD! Now buy points, condensor, cap, rotor and wires (and probably a timing light).

 

Yours is a HIFF type carb you will need to remove this from cyl head and give it a clean then theres a ajuster screu insibe to open jet and then theres a screw on the L/H side looking into engine bay by the two pipes to ajust the mixture....this web site may help................
http://www.sucarb.co.uk/TechnicalDetail.aspx?id=74

 

Thanks for the info and links. I changed the plugs today. Pic link below. Car is definitely runnng rich I think. Plugs were pretty black.

http://picasaweb.google.com/pbhathen...t=embedwebsite