Using a digital multimeter

ILLaViTaR · 14-06-2007, 05:32 PM

I borrowed a multimeter from my school and was wondering how to use it.

Since my car is running like crap I need to check the TFI and a lot of other things apparantly.

The thing that confuses me is the dial on it there's tonnes of different options

like for ohms you got 200k, 20k, 2k, 200, same with everything else.

I'm checking the leads now and picked 20k and it came up as 7.97 on the multimeter which is really weird cause that's around 10k below spec

efgiar · 14-06-2007, 06:25 PM

the ohms reading for leads depends on the brand and what kind of leads they are, 8kohms isnt a bad reading, if the ones of similar length are all around that reading then it will be fine, its the ones that are open circuit or read too high that give you grief.

accurate1 · 14-06-2007, 09:22 PM

7.97 equals 7,970 ohms or 7.97Kohms so the leads are OK.

94EDxr6 · 14-06-2007, 10:02 PM

like for ohms you got 200k, 20k, 2k, 200, same with everything else.

I'm checking the leads now and picked 20k and it came up as 7.97 on the multimeter which is really weird cause that's around 10k below spec

what resistance are you looking for in ohms? If you're testing your leads they should have very little resistance. I'm not a mechanic but it would have to be below 0 ohms. Put the setting on 200. Whatever comes up then will be your resistance.

sphell · 14-06-2007, 10:06 PM

Quote:

Originally Posted by 94EDxr6

I'm not a mechanic but it would have to be below 0 ohms.

And I'm no rocket scientist but how is that possible? :togo:

needfordspeed · 14-06-2007, 11:20 PM

Quote:

Originally Posted by sphell

And I'm no rocket scientist but how is that possible? :togo:

It's a streamlined butterfly, no resistance what so ever!

**aussiblue** · 14-06-2007, 11:30 PM

No; most modern leads do have resistance (to suppress radio noise) and carbon ones are typically as high as 40K ohms. If you had old fashioned noisy copper wire core lead you might get reading less than 10 ohms. Ford ones should have a max resistance of 21 K ohms and 7 k ohms is right on for new leads.

ILLaViTaR · 14-06-2007, 11:31 PM

Yeah leads look fine.

How do I check the TFI module with a multimeter?

Do I have to disconnect the negative battery terminal?

I done that and probed pin 4 and 5 and nothing happened.

My cars been running like crap for a week. Also found out that the transmission is leaking oil and it was only serviced 20 000k's ago. It's leaking form the oil pan so it's just a retightening I think.

**aussiblue** · 14-06-2007, 11:34 PM

see http://www.therangerstation.com/tech...iagnostic.html you need to remove the module to test it.

ILLaViTaR · 14-06-2007, 11:49 PM

hmmm.

How do I check for spark in the spark plugs?

My problem is the engine idles low and runs rough (like when it's misfiring but I got the firing order correct).

**aussiblue** · 14-06-2007, 11:55 PM

To test the leads are supplying spark remove fuel pump relay and get a good used spark plug open the gap up to about 3mm and put in each lead in turn allowing the plug to ground against the engine head or block and watch for a spark. To test plugs remove each plug in turn and do the same thing (but leave gap at specifications).

**aussiblue** · 14-06-2007, 11:56 PM

Also check air or fuel filter is not clogged - both will give the symptoms you describe.

accurate1 · 15-06-2007, 12:00 AM

[QUOTE=ILLaViTaR]
How do I check the TFI module with a multimeter?

If the car is running why do you want to check the TFI module?

ILLaViTaR · 15-06-2007, 12:07 AM

I was told to check it. So since it's running I'm guessing the coil, distributer and TFI are fine??? (excluding ignition timing since I hacn't checked it yet).

I took the air filter out and ran it for around 20 seconds and same problem.

I'll also mention that when I put the leads back on ever since then when I start it the crank sounds extremely weak and unsmooth.

Im very happy it doesn't sound mechanicallly related. (I've checked timing chain and it's fine and rocker gear seems fine by the looks of it).

**aussiblue** · 15-06-2007, 12:11 AM

Is the distributor cap sitting tight and in locating notch? Is king lead (central HTlead) still in coil at coil end?

**aussiblue** · 15-06-2007, 12:13 AM

Check there is no corrosion in distributor cap where leads plug in and all leads are pushed right down on the spark plugs (I guess you didn't use the right lead removal tool to pull the leads of the plugs and didn't put dielectric paste on each end of the leads when plugging them in again - if so you might fine a lead had moved up the HT lead's plug boot so it cannot clip fully onto the spark plug).

A tool like this:

ILLaViTaR · 15-06-2007, 12:14 AM

Coil lead is in both ends.

unsure about distributer I'll have to check it out tomorrow.

I don't think I've ever touched it until now.

It's been happening ever since I changed the thermostat which makes no sense.

I ran it for around an hour in total with the new thermostat idling and the next day I started the car to find this problem

**aussiblue** · 15-06-2007, 12:21 AM

Did you follow the air bleed procedure after replacing the T stat? No chance you put the T Stat in upside down is there?

More likely you spilt coolant into the TFI module plug and socket at the distributor end as it's under the T Stat. Unplug TFI plug and after drying out with WD 40 or CRC fill socket with thermal paste per factory manual specs (Unick from Altronics. Jaycar or Dick Smiths is cheaper than the Ford supplied stuff).

**aussiblue** · 15-06-2007, 12:23 AM

ILLaViTaR · 15-06-2007, 12:26 AM

Hmmm what was the air bleed procedure again?

It might've spilt whilst the thermostat was out when flushing (water was leaking out due to no seal).

Also there's no way I put it in upside down.

**aussiblue** · 15-06-2007, 12:37 AM

Quote:

Hmmm what was the air bleed procedure again?

I told you here; http://www.fordforums.com.au/showthr...ight=air+bleed

**aussiblue** · 15-06-2007, 12:38 AM

I would pull the plug that goes into the TFI module and see if there is any coolant in there and if there is a liberal amount of thermal grease (white goo) in the socket. 5 min job.

ILLaViTaR · 15-06-2007, 12:46 AM

Oops sorry I ddn't do all of that correctly.

I put in the thermostat and then filled it up.

So it's probably got an air lock, I'll drain it all, and refill it properly.

I just realised how *** stupid that was, Since I drained it there was probably no water in the block and when it sensed the air being hot in the block it mustive released the water into the head, it was rather warm before it went in though but hopefully I havn't blown a bloody head gasket.

Would a blown head gasket or worse a cracked cylinder head explain the symptoms that I'm having?

I aint getting white smoke though

**aussiblue** · 15-06-2007, 12:56 AM

Lets pray it's an air lock.

ILLaViTaR · 15-06-2007, 01:02 AM

Yeah, I don't see any coolant dripping form the head gasket although it is extremely hard to see the gasket itself.

There's no way to be sure if it's the gasket unless I actually take the cylinder head off is there?

Man taking the rocker gear, and manifolds off is gonna be an extremely frustrating job.

ILLaViTaR · 15-06-2007, 01:07 AM

This also explains why it took 1/2 an hour for the thermostat to open... ****.

Could have this screwed up the whole engine form overheating???

I'm trying to think worst case scenario.

Headgasket shouldn't cost me to much if I do it myself, I'm thinking if I screwed the whole cylinder head or worse the whole crankshaft part form overheating.

**aussiblue** · 15-06-2007, 01:10 AM

You should be Ok provided it hasn't overheated too much since. The air lock usually doesn't blow a head gasket for some time esp in winter.

**aussiblue** · 15-06-2007, 01:12 AM

More likely coolant in the TFI connector socket.

ILLaViTaR · 15-06-2007, 01:24 AM

Hmmm yeah.

It's not the fact of an air lock I think. It's the fact that I filled it up from the surge tank and not the thermal housing. The thermostat would not open till 91 degrees yeah?

Meaning that the thermostat was blocking all the water from the head. The head being empty (since I drained flushing liquid from it). The air in the empty head would have heated up to 91 degrees and opened the thermostat letting only warm water into the extremely hot head damaging it.

Also water absorbs heat and air doesn't so the engine would have been extremely hot when it let water in?

**aussiblue** · 15-06-2007, 01:27 AM

Lots have people have got away with doing this and it is usually only the overheating from the air lock that eventually creates a problem with a blown head gasket. Don't worry unduly yet and just go through the air bleed coolant filling process before it is too late.

If the T Stat had a Jiggle pin a (best) or bleed notch (not as good) some coolant will enter through that and more through lower raditor hose (mostly there) as some air will bleed through the jiggle pin or bleed notch and let coolant enter fromm below. However the bleed notch and jiggle pin bleed much too slowly to let all the air out and some will be still trapped in the engine block and mainly in the head. Remove T stat housing and T stat and start correct filling and air bleeding procedure again to fix it.