[Rohan]

Hi,

Sorry for the long post. I am having a couple of problems with my Suzuki sierra (1990, SJ70), which have all started in the last week. Up until then she has run well. But has recently developed the following issues. I am after some suggestions for what to check



1. Temperature gauge isn’t working accurately (only reads just above cold mark when at operating temp)
2. High idle when cold or warm – sits at 2000rpm when no load is on the engine. Turn on headlight or heater fan and it doesn’t change
3. Intermittent problem starting – hit the key and the radio goes off but the starter doesn’t turn. I roll start it and the problem goes away for a few days.


Background:

A week ago I went to the coast stopped for fuel and couldn’t start. Wiggled the wire to the started solenoid, gave up and roll started it. Going home I noticed that the temperature gauge wasn’t reading correctly. The car didn’t feel hot and still had plenty of coolant so I assumed I must have disturbed a wire from the sender while fiddling with the starter wire. Got most of the way home and noticed that it idled at 2000rpm.



Next day I decided to test the temperature gauge using a test light (as described in the workshop manual). Bulb in the test light was dim but this moved the gauge in the cab so assumed it was the sender. Bought a new one but this didn’t fix the problem.



To try and fix the idle issue I cleaned the carby and replaced the vacuum lines one at a time in case there was a vacuum issue (had read that could cause issues). The issue didn’t go away but she runs harder now. Next step is to adjust the idle screw but as the machine was running well until recently I haven’t wanted to adjust that in case its something else that’s going on.



To try and fix the started I made up a clicky start relay thing based on some instructions I found online. This appeared to work but it played up a day later. At the moment I have removed the relay and am back to the original wires, which has worked for the last 2-3 starts. Based on this behaviour I am guessing it is a dodgy connection in the wire running to the starter solenoid, so will replace that on the weekend.



The only other idea I have is that this could all be due to a poor earth connection or something equally silly.



Any suggestions appreciated



Thanks

[Santos]

Earth connection is a big possibility, do you have an extremely thick black cable running from the negative terminal to the firewall? I recommend something as thick as the cables that run to your starter. Also check that your ground/negative running to the starter body is bolted down rock solid. I've had them work themselves over time, in the end the solution was to find a longer bolt so it could grab more thread and use metal washers and or nuts to take up the slack so it would be firm. If i was to do it again i would install a longer stud and use a single nut and washer. This will make installing and removing the starter easier.

I had starter issues over a year, i could only turn the car on regularly by running a thick wire from the battery to the starter terminal.
Only when i wired fresh wires and socket for the relay and wiring the earth and power directly to the battery have i been able to start from the ignition.

2000rpm sounds like something is getting stuck

-confirm your choke is not stuck closed

-check your throttle cable is adjusted correctly, this takes two people, one person to work the acceleratr pedal and one to visually confirm the primary throttle opens completely. Always disconnect the throttle cable when checking or adjusting other things.

- check that your PCV valve and EGR valves are working correctly (huge vacuum leak sources that can be overlooked

- Check your idle up solenoid is not stuck 'on', this is at the front of the carburetor (blocking the fuel bowl screws) its purpose is to open the throttle a little when you turn on your headlights to compensate for the extra load, many people disconnect or ditch this feature completely

-check your distributor is set up correctly and you haven't advanced it somehow, in fact make sure its set up correctly and not a few teeth out, the factory manual instructions are actually 180 degrees out! I still follow them but once i line up all the marks i rotate the crank 540 degrees (360 to make sure the marks line up again, then 180 so that the camshaft marking is facing down) you can also visually confirm with the valve cover off , you can also get a leak from the distributors actual vacuum actuator, if its faulty.

-Lastly how far is your HOT IDLE SCREW turned in? i find if you wind it ahead, all the way off where it touches the throttle lever it only needs a few turns once it makes contact, if you are winding it in excessively chances are your ACTUAL IDLE SCREW is way out of speck, as most of them have a tamper-proof head for emmission reasons its best to replace it with an older one that can be easily adjusted. mount the carb 180 degrees so the floatbowl is facing the firewall, hook up all your vacuum lines, follow the service manual tuning instructions with a completely warm engine. make sure you get a vacuum gauge and timing light, once you are idling 800-900 make sure your timing is correct at 8-10 degrees advance with 20-21 degrees vacuum.

A completely warm engine is one that has been driven for more than 15 minutes at low road speeds, this make sue everything is warm and at EVEN operating temperature for tuning, not just your temp guage and pistons. Chances are the HOT IDLE SCREW will be the thing that fixes your problem however i mention it last cause it will compensate for a lot of the other things and over time will rob you of performance . This creep up of its settings will make the setup filled with strange fluctuating problems that will convince you its possessed and blame its design rather than your lack of mantenance and understanding of its simple settings.


BONUS: Look up 'Smoke generator Vacuum leak detector' there are quite a few youtube videos, i wish i had stumbled across this method sooner for finding vacuum leaks as i am not a fan of the starter fluid method. Building my own machine soon but here is an even simpler method with a cigar

[Rohan]

Thanks for the detailed reply. I will work through those suggestions and see how we go. The earth lead to the firewall is just the thin factory one so that's a possible issue. Thanks

[Santos]

was revisiting the carburetor manual and noticed there is a third FAST IDLE screw

For the sake of clarity when i say HOT IDLE screw the factory manual list it as IDLE SPEED SCREW
and the REAL IDLE is listed as IDLE MIXTURE SCREW

also make sure float is set at the correct height, float level changes fuel ratios. If the float level is too high it pushes more fuel dwn the venturies or tooo low it leans out etc.;

[Rohan]

OK thanks. I have been reading and rereading the manual and will have a good look on Saturday. The terminology takes a while to get my head around but I am getting there. My plan is to check everything (earth, vacuum lines, pcv, float, etc) then if all else fails start adjusting things.

I will let you know how I get on.

Thanks so much for the suggestions. Really appreciate it

[Rohan]

Went over the above list. Found another iffy vac hose and a heap of mud etc which I removed. The revs at warm idle are now at 1400 rpm. Still a bit high but improved a lot. Will adjust the hot idle screw to get them down a bit more.

Also added larger earth which hasn't fixed the temp gauge or starter issues. Will keep cleaning and testing and work my way through the possible issues. Thanks for the suggestions

[bumstein]

In regard to your temp sensor, make sure it's reading correctly to begin with. If you can borrow (or buy a cheap one) sensor and gauge to hook up in the radiator hoses then you'll see if it's giving you the right info.

If it's not then your fault finding the sensor and wiring. If it is then your fault finding the cooling system.

Have you replaced the thermostat? I check them my dropping them in a pot with hot water. I keep adding boiling water until it opens, I have a thermometer so I know what temp it's opening at. If it's not doing it's job replace it.

In regards to earth, a large wire is good but I'd still be putting a multimeter from the sensor to the negative terminal of the battery and see if there's some resistance in the circuit

[Rohan]

Thanks. I replaced the thermostat around Christmas when I last did the timing belt but can easily check it.

I will play a bit more tomorrow.

[bumstein]

You'll get there!! Some of these gremlins take much time and thought to narrow down the issues.. rewarding once you find it

[Rohan]

OK. So replaced the thermostat and discovered the old one had broken one side of the spring retainer in half so was stuck open. Havent taken it for a test run yet but I am hopeful it will improve things. Definitely worth finding anyway

[bumstein]

Excellent result!!!

[Santos]

[Rohan]

Took it for a run. Idelling correctly now. Thanks for the help.

[bumstein]

And the temp gauge?

[Rohan]

Temp gauge played up due to thermostat being stuck open. So no problem with it as it was reading correctly. The motor just ran cold the whole time. Starter issue appears to be a dying starter motor so will replace it soon and she will be all good. I have 340k km on her so cant complain too much

[bumstein]

Fantastic result!!

Cheap and easy fix.. good work

At 340 the motors still young. Keep giving it lots of love and it will keep working