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post #1 of 26 (permalink) Old 12-17-2011, 10:26 PM Thread Starter
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sensor question

The Hall Effect Sensor ,what are the symptoms of a bad one? 3.8 1993
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post #2 of 26 (permalink) Old 12-18-2011, 12:58 AM Thread Starter
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post #3 of 26 (permalink) Old 12-18-2011, 10:08 AM
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Quote:
Originally Posted by 1956pack View Post
I dont think that's very helpful to folks with same -whatever- problems you are having.

BAD: No tach bounce on crank, no spark from coil. 12v read one side of coil. Same symptoms with SPOUT disconnected. No {infinite} reading, or dead short, when ohmming out sensor.
Check back of ign module, if grease dry, may be ICM bad.

Erratic: Erratic tach and spark. Watch coil and all plug wires in dark when crank. Check dist shaft for sideways slop.

Never hurts to have used working dist and ICM on hand. Can hook up dist to check ICM and coil without installing it.

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post #4 of 26 (permalink) Old 12-18-2011, 11:41 AM
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Usually when I run across a bad one, the symptoms are pretty simple:

Vehicle won't start due to injectors & plugs not firing or intermittently firing.

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post #5 of 26 (permalink) Old 12-18-2011, 11:53 AM Thread Starter
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I have a warm start issue,engine runs great other than that,I'm at 90k,top of engine is rebuilt, I'm pretty sure fuel pump must be going bad. just looking at other stuff before dropping the tank! fuel pressures just not there, after 15 min drive and restart,stumbles and recovers and drives fine,its just when it sits,pressure in fuel system doesn't hold for restart.
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post #6 of 26 (permalink) Old 12-18-2011, 01:27 PM
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Originally Posted by 1956pack View Post
I have a warm start issue,engine runs great other than that,I'm at 90k,top of engine is rebuilt, I'm pretty sure fuel pump must be going bad. just looking at other stuff before dropping the tank! fuel pressures just not there, after 15 min drive and restart,stumbles and recovers and drives fine,its just when it sits,pressure in fuel system doesn't hold for restart.
If it's "pressure in fuel system doesn't hold for restart", I'd check the (easier to get to!) Fuel Pressure Regulator first, since we've got a return fuel system (pump runs all the time, the FPR bleeds excess pressure back to the tank).

Since its purpose is to bleed pressure off, and that's the problem, I'd see if it's bleeding TOO well first

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post #7 of 26 (permalink) Old 12-18-2011, 01:42 PM Thread Starter
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car does have a slight miss occasionally. like when I'm at a red light I can feel it, has had that prob for years, that's why I was thinking Hal effect sensor .plugs,cap,wires replaced also coil, cleaned all sensors.
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post #8 of 26 (permalink) Old 12-18-2011, 03:22 PM
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Quote:
Originally Posted by 1956pack View Post
car does have a slight miss occasionally. like when I'm at a red light I can feel it, has had that prob for years, that's why I was thinking Hal effect sensor .plugs,cap,wires replaced also coil, cleaned all sensors.
Put it on a scope or graphing multimeter and see if there are any irregularities in the signal wave generated by the hall effect.

I doubt you will find it bad. A hall effect doesnt produce a strong signal at low RPM's, so if it were in fact bad, it probably would not allow the engine to start.

Last edited by dDUBb; 12-18-2011 at 03:27 PM.
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post #9 of 26 (permalink) Old 12-18-2011, 04:00 PM
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A hall effect doesnt produce a strong signal at low RPM's, so if it were in fact bad, it probably would not allow the engine to start.
Mmm?

Seems like that's one of the strong points on the Hall Effect sensor - it's typically driven internally to full swing on almost ANY change in magnetic field, so it produces the same strength field no matter how rapidly it's changing (as opposed to a simple magnetic reluctor, whose strength of output DOES depend on how quickly the field changes).

See, for instance, http://content.honeywell.com/sensing...l/chapter2.pdf for a good explaination (it's the strength of the magnetic field, not the rate of change, that affects the Hall Sensor output. A straight coil? Changes output depending on the rate of change.)

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post #10 of 26 (permalink) Old 12-18-2011, 04:26 PM
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Originally Posted by RalphP View Post
Mmm?

Seems like that's one of the strong points on the Hall Effect sensor - it's typically driven internally to full swing on almost ANY change in magnetic field, so it produces the same strength field no matter how rapidly it's changing (as opposed to a simple magnetic reluctor, whose strength of output DOES depend on how quickly the field changes).

See, for instance, http://content.honeywell.com/sensing...l/chapter2.pdf for a good explaination (it's the strength of the magnetic field, not the rate of change, that affects the Hall Sensor output. A straight coil? Changes output depending on the rate of change.)

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Its old technology, thats why newer cars use an MRE sensor, digital output.
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post #11 of 26 (permalink) Old 12-18-2011, 09:50 PM Thread Starter
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I'm thinking fuel pump,starting to starve for fuel at cold start. eventually starts
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post #12 of 26 (permalink) Old 12-18-2011, 11:43 PM
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I'm thinking fuel pump,starting to starve for fuel at cold start. eventually starts
Do you have access to a Fuel pressure gauge ? Many parts stores rent these, they arent very expensive to buy either. At least Ford was nice enough to put a valve on the fuel rail to make checking pressure easy.
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post #13 of 26 (permalink) Old 12-19-2011, 09:26 AM
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This thing is all over the place. It would be nice if there was an orderly method to solve the problem.

We could start by assuming a good stock Hall Effect pickup sensor will work even with low battery and crank speed ..BECAUSE IT DOES!!! I have over 20 years experience to state that and so do many of you.

FIRST: Because it takes about ten seconds. Pull the vac line to the regulator. If there is fuel in it, that will cause hot start and possible fuel pressure problems. Replace FPR.

SECOND: Do you know about the hard start drill? Most PCM's are programmed to act like a carb, by looking at the throttle position during crank.
- at WOT {floored} injects LESS fuel to clear a flooded condition
- if TPS {pump accel pedal} voltage varies, will send MORE fuel than normal.
BTW: All that also suggests a bad TPS will cause hard starts and performance issues. Usually, but not always, along with idle speed problems. How IS your idle?

Also: Key on till pump stops key off then on again wait one second and crank. If works good then you have weak pump or serious leakdown.
Get the Gauge and check prime state pressure. Then leakdown. If it takes two primes to get to nominal 40 lb OR if it drops to under ten in a couple of seconds you have a real problem

Assuming you have changed fuel filter and CHECKED the old one for blockage and your fuel pump isnt growling at you with the typical worn motor bearing noises, it probably is not the pump. Walbro's dont just give up that easy, unlike Airtex.
I pulled my old one at about 190 Kmile..when it started growling but there were no crank or performance issues. And the rest of the assembly was still good. It's possible your tank is dirty and the pickup sock is covered with gunk. If so your filter should have been restricted as well. Mine on the other hand was clean as a pin. I quit changing fuel filters years ago because the old ones always flowed free. Now only when I get a different car. Because I only buy gas at one brand and hi-volume stations at that.

- ignition-
What fails with age and not just miles? Coil, ign module {heat sink grease} and wires.

Do the O-Dark-thirty test and watch the engine run in the dark. You should see no fireworks.

Pull the ign module itself off the mount. Should be greasy grease on back not cake. If cake replace ign module.
Pull distributor cap and wiggle rotor .. should be no lateral slop.
On that subject DO NOT buy just any brand cap rotor and wires. If at Autozone go up one price tier at least.
NOT Wells brand.

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post #14 of 26 (permalink) Old 12-19-2011, 01:22 PM Thread Starter
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Idle is fine,performance good,you can floor it and no miss's, nothing unusual,looked at the cap and rotor ,all good,no sparking or arcing at nite, along with hot start issue now stumbling on cold start, so whatever is causing my problem is getting worse and will soon go out.I'm going to not drive it until its fixed,afraid I'll get stranded, neighbor Rick who was a GM mechanic for years and had his own shop tells me fuel pump going bad,that's usually the prob, don't have any FP gauge. engine itself is pretty good,I did a full hg replacement myself at home 3 years ago.
one question on fp regulator ,do you rebuild it or replace entire unit?
also if the fuel pump is the culprit,seems the car would cut out really bad when you floor it.it doesn't? only starting issue stumbles then recovers around 15/20 sec.
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post #15 of 26 (permalink) Old 12-19-2011, 02:16 PM
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Fuel pumps have a check valve in them that sometimes go bad this will bleed off the pressure when the pump is not running very quickly. If it is in fact leaking, it will take longer to crank the engine at start. Doesnt mean the pump itself is bad .. it just doesnt build up pressure quickly when you want to start the car.

Tools are useful .. I suppose you should find a fuel pressure gauge if you want to know for sure. Youre skipping BASIC testing and jumping into the electrical engine controls.
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post #16 of 26 (permalink) Old 12-19-2011, 04:21 PM Thread Starter
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Just went out and started fine. checked fuel press regulator ,no gas in vac line.
talked to Rick asked again,signs of bad fuel pump,loss of power,missing under load,start issues.have plenty of power ,no missing under load. only warm start issue,
he say's maybe ign control module attached by radiator passager side. think I'll get a pressure gauge and check system cold and aft warmed up,plus hold pressure spec's
can't afford to shotgun parts at it haha!
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post #17 of 26 (permalink) Old 12-19-2011, 08:33 PM
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Just went out and started fine. checked fuel press regulator ,no gas in vac line.
talked to Rick asked again,signs of bad fuel pump,loss of power,missing under load,start issues.have plenty of power ,no missing under load. only warm start issue,
he say's maybe ign control module attached by radiator passager side. think I'll get a pressure gauge and check system cold and aft warmed up,plus hold pressure spec's
can't afford to shotgun parts at it haha!
The "cheap" way to shotgun is have a identical good running vehicle to test parts from. Just switch over what you suspect until you hit the part.

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post #18 of 26 (permalink) Old 12-20-2011, 01:03 AM Thread Starter
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Finally have a f pressure gauge ,will test tomorrow and post results.now for a cold one!
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post #19 of 26 (permalink) Old 12-20-2011, 01:07 AM Thread Starter
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The "cheap" way to shotgun is have a identical good running vehicle to test parts from. Just switch over what you suspect until you hit the part.
Wish I had another one but don't. I bought 2 300e cars last month so I can do that to those cars!
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post #20 of 26 (permalink) Old 12-20-2011, 01:05 PM
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I have a warm start issue,engine runs great other than that,I'm at 90k,top of engine is rebuilt, I'm pretty sure fuel pump must be going bad. just looking at other stuff before dropping the tank! fuel pressures just not there, after 15 min drive and restart,stumbles and recovers and drives fine,its just when it sits,pressure in fuel system doesn't hold for restart.
This sounds like a low fuel pressure problem. Warm start issues are usually not ignition related because warm combustion should occur easier.

Check your fuel filter first. Be careful to let the pressure subside or you will get sprayed in the face when you release the filter lines. (Speaking from experience). If you do get sprayed flush your face and eyes with a water hose thoroughly.


After you change the filter, if there is no change, just change out the fuel pump. Even with 90K a fuel pump can start to go bad.

It is unlikely that your fuel pressure regulator is causing this issue but a quick test is to unplug the vacuum line if there are doubts. This will increase the fuel pressure.

Make sure to post the solution when you figure it out.
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post #21 of 26 (permalink) Old 12-20-2011, 02:45 PM Thread Starter
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Ok here are the results with gauge on fuel rail fitting
Completely cold over nite 0 PSI

start ,holding at 31 PSI and goes up a little when I increase rpm

warm car up for 10 min, engine off holding at 30PSI,after 3 min 30 PSI, 5 min 29 PSI, 8 min 21 PSI, 10 min,20.5 PSI. Manual has pressures with vacuum hose on and off,not sure which vac hose their talking about? left it on.
tried restart once warmed ,car stumbles 10/15 sec then recovers
sometimes its worse,lots of cranking and sometimes its not
car has had a intermittent miss for years,not sure what that's about?
could a leaking injector cause the warm start prob? just thinking about that missing and warm start issue being related,fuel leak thru injector and flooding spark plug

so your saying disco vac line from FPR that goes to top of manifold,and restart when warmed?
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post #22 of 26 (permalink) Old 12-20-2011, 11:08 PM
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Pressure sounds about normal ( except for the bleeding down part ) .. a leaking fuel injector could cause a misfire also. Ehh .. I usually remove the fuel rail with the injectors still attached to the rail and pressurize the system to see if any are leaking. Otherwise it would be leaking at your pump itself.

If you prime it a couple times up to @ 30 psi before you actually try to crank it that would determine if its a fuel issue causing it to not start.

A leaking fuel injector shouldnt cause a no start issue, it doesnt sound like its leaking that bad, but 0 PSI in the rail means no fuel to inject during cranking ..


ps. I hate working on mercedes. I cant tell you how much time I have spent looking through the Werkenstatinformationsystem
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post #23 of 26 (permalink) Old 12-21-2011, 12:39 AM Thread Starter
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0 psi is car sitting over-nite. I'll try tommorow starting it up ,let it warm up,shut her down, relive pressure at schrater valve,install gauge,then turn key on few times and see how much pressure I've got. I have no problem changing the pump out if that's the problem,probably is,the manual says Should have 30 to 40 psi engine running
today doing some Xmas shopping and driving around floored it with no problems.I just don't understand if FP was going bad wouldn't it miss alot
as far as the Mercedes I'm learning on these and boy they do have some weird problems,but I fixed my sons 91 300e 3.0 had a blown head gasket. not a horrible job but not as bad as his electrical short behind the dash,that was 2 weeks of joy!

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post #24 of 26 (permalink) Old 12-21-2011, 09:56 AM
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First: If you dont have problems with WOT acceleration, it probably isnt a bad fuel pump, providing it doesnt leakdown real fast.

Second: Do the pressure/leakdown without engine running, just from 1 or 2 prime cycles or from bypassed and constant run. Understand that when you read it -running- you have to figure in manifold vacuum. Lots of other things affect manifold vacuum. Finding the nominal pressure at atmosphere rules those out.

'Gm Mechanic' sorta puts him as a civilian here esp if he sees a lot of Vortec (60 lb) systems. Weak FP happens a LOT {but still not as much as some think} on those. In relative terms, an aquarium pump will work in a ford.

Speaking of that.. just found a video that showed a bad {cracked diaphragm} FPR in a vortec 4.3 that passed leakdown.
That means it COULD happen in a Ford, too. ANY fuel at all in the vac port!

OTHER things: Plugs. wires. cap rotor. Unsuitable plugs - like Bosch Plats, for example- display intermittent, or constant miss given cylinder, in 'low load cruise', work fine under load.

Finally: Do the HARD START drill!
PEdal to floor sends less fuel.
Pumping pedal sends more.
Do the WOT first. If it starts, then you have a fuel leak into intake {like from the FPR}, or leaky injector. Read the plugs.

If starts when pumping, then either Pressure is bad, or you have vacuum leak somewhere.

Vacuum leak also causes low load miss.

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Last edited by pettyfog; 12-21-2011 at 10:12 AM.
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post #25 of 26 (permalink) Old 12-21-2011, 04:58 PM Thread Starter
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Ok ,ran test again,with KO 2-3 times pumps up to 39psi,aft 5 min psi drops below 30,checked vac hose off fuel pressure regulator and found gas dripping out of it!
so that must be the prob. thankfully its a cheap fix! will get one and post results
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post #26 of 26 (permalink) Old 12-25-2011, 08:05 PM Thread Starter
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Replaced P regulator,seems to have fixed the prob,old one didn't hold the pressure well. about 3 hrs work.have to remove fuel rail to get to the 3 Allen screws that hold regulator on. vac lines breaking left and right!
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