Stump The Technicians--Contest Rules Are Here!

Mr_Shiftright

If the fuel filter worked for a short time, one would have to conclude that there is some debris from the gas tank clogging the new filter, since the new filter was the only change to modify the situation that we are aware of. Or maybe some kind of weird collapse of the "ribbon filter" that is sometimes attached to fuel pumps that are installed inside gas tanks.

bobistheoilguy

you got it. of course i spent 2 hrs chasing my tale cause he was adiment about it was a new filter and couldn't be it..

7937

Mr.Shiftright, I'll take a stab at your problem with the Mercedes Diesel not switching off. I've never worked on diesels but I'd hazard a guess that the "ignition" key switches off a solenoid that cuts off the fuel to the injectors. Seeing as there is no electric ignition on a diesel, that seems to be the only thing that would stop the engine. In this case I'd say that there is something faulty with the solenoid or its circuit.

bobistheoilguy

there is only 2ways to shut down this car, shut fuel or air down. since the key is involved, it has to control an electronic device.. either the injectors are electronicly controlled (unlike a chev used a mechanical pump for injectors) or a control to shut down the air intake. my first thoughts would be a shutdown circut for the injectors was failing.

bobistheoilguy

as the older car with the bad fuel filter i had a ford motor home, 460? i think, anyway, it was a big one.. started pulling hills, and was starving for gas going up the hill, then as time progressed, it got to a point where they were pushing on the gas and barely moving. at idle, you could race the engine and it would back fire and pop through the carb. ignition seemed to be fine.. fuel pump fine, filter fine..

where would u go on this one.

tboner1965

The injectors opened when the injector pump (which also pumped fuel) pumped enough fuel at pressure to "open" the injector.

The injector pump had a built in "fuel shutoff valve" which I believe was solenoid operated.

The throttle connected to the injector pump, and not to a throttle plate like you see in carburated and fuel injected gasoline engines.

So this solenoid/shutoff valve was probably bad.

TB

Mr_Shiftright

Well you are all close but the interesting thing is that there is no electric solenoid on a 300D. Some diesels may indeed have one but not this car. This is what makes the diagnosis so strange, because you can't see some conspicuous solenoid anywhere in the fuel system.

In fact, you can disconnect the battery and throw the alternator over a fence and the engine will continue to run!

Any other ideas on how fuel is shut off by the key?

bobistheoilguy

do with a computer or i/o box hooked to a computer. in this box would be a circut that may had a direct short for keeping the fuel system energized.

or would it have something to do with oil pressure?

what year is this car?

0patience

The 300D uses a vacuum operated fuel stop.
If it ain't working, either the vacuum pump,the fuel stop canister, the vacuum hose or the ignition switch are bad.

Mr_Shiftright

Exactly. There is a vacuum switch connected to the ignition lock. Unfortunately, the same vacuum system works door locks, etc., so there could very well be a connection between your not being able to lock the car OR shut it off! This also makes the problem tricky to fix, as you may not know where the vacuum leak is. I've heard of some mechanics blowing smoke into the system to trace it!

dpwestlake

Whoever said that it was a combination of the fuel tank venting and a weak needle valve in the carb causing the pickup to fill the engine with gas was correct.

It happened when the truck was parked in the hot garage for a weekend with a full tank. Heat expanded the gas and forced it past the needle valve and down the intake manifold, into the cylinders where it both filled up the crankcase by seeping past the rings and caused hydraulic lock in the cylinders.

tboner1965

I was called to a meeting at a customer site 25 miles away. I leave and my car seem to cut out on bumps. The check engine light will come on as the engine cut's out.

About halfway into the trip, the problem "goes away"

I suspect the problem and replace the component. The problem never comes back. What did I replace?

87 LeSabre, with about 85K miles on the clock.

TB

tboner1965

I surmized this would be a component that could "get better" with a drive.

TB

ezaircon4jc

Got one. 1986 Mercury Sable, 3.0, auto. Under hard acceleration the A/C would shift from the vents to the defroster outlets. Lift or accelerate "normally" and everything was fine.

7937

Leak in the vacuum system controlling the flapper doors.

0patience

Agree with 7937, but most likely the check valve in the brake booster is shot.
The vacuum system uses the brake booster as a resevoir for the vacuum system under acceleration.

javadoc

Was it a temperature sensor, or O2 sensor? Long shot, but I thought I'd play. Then... once we've solved your question, I've got a doozie (blatent challenge to Shifty)!

/javadoc

Mr_Shiftright

And I've got a related one for you. Where does the term "doozie" come from?

tboner1965

A guy in the town I grew up in has one on display at the Gilmore museum.

I was too poor to attract the attention of him or his daughter that was a couple years younger than me.

The problem with my car. Bad battery. The drive recharged the battery, so it worked. I took it for testing and it did test bad. They weren't trying to sell me a battery either, they had to replace it under warranty.

Cheers,

TB

javadoc

The low voltage was both tripping your CEL and killing the car. Wow, sometimes it's the basics!

/j

javadoc

I just found out the answer to this one today (after over a week of stumping my mechanic), so:

1996 Volvo 850 Turbo, 75k (my beloved Volvo, yes)

Symptoms:
1. CEL lights up
2. Car won't idle
3. Car runs fine (sans idle) until warmed up..
4. After warm-up, car hesitates badly
5. Hesitation accompanied by "rotten egg" smell

No, this isn't the obvious problem, or the obvious one I thought it was. Okay, make it run champs!

/javadoc

shipo

Oddly enough, I looked up the term Doozie in "Websters" and came up with the following:

Etymology: perhaps alteration of daisy
Date: 1916
:an extraordinary one if its kind.

Hmmmm, me thinks that Webster and Co., et all have missed the boat on this one. If I remember my history correctly, the Duesenberg Automobile and Motors Company was established in 1920 in Indianapolis, and depression era folks would call the rare Dusenbergs cruising around "Duesies".

In this case, I think that Shifty has it correct and Webster blew it.

As for the smelly Volvo, I typically attribute the "rotten egg" smell to a messed up Air to Fuel ratio (ie. messed up air mass sensor, wasted air filter or some other obstruction in the air intake system, etc.). That said, I suspect that that is too easy of a solution.

Best Regards,
Shipo

javadoc

My first thought too, and unfortunately not the solution. Good first try!

This won't send anyone too far off the scent (pun intended), I hope. The car was spitting out the code for a bad MAF sensor, but it wasn't ultimately the problem. My mechanic wanted to blame it on my K&N cone filter, lol.

/j

tboner1965

In this case, I think that Shifty has it correct and Webster blew it.

TB

tboner1965

Let's think out loud here and maybe I'll come up with an answer...

Runs fine when cold, but after warm...

Isn't there some sort of fuel enrichment injector on this bad boy. It adds extra fuel when the engine is cold.

I'm going to say coolant temp sensor, or intake air temp sensor is bad. Engine never knows it warmed up, so it keeps enriching the mixture.

I'm leaning strongly towards the IAT sensor since the computer doesn't think the MAF is working correctly.

TB

jlflemmons

Bad temp sensor. Iron Duke 4 used 3 sensors in '84. One for the guage, one for the ECM, and one for the electric cooling fan. If the one for the ECM goes off-calibration, the engine can think it is a lot cooler than it is. Runs super rich for the temp causing a bad or high idle and stinks big time once warmed up. The aformentioned rich condition.

Jim

javadoc

Wow, tb, you can be my Volvo tech now! The problem ended up being the AIT sensor, but for some reason the codes didn't point in that direction, so the mechanic disregarded that option because he was relying on the computer's code data. The codes pointed to the MAF and then when that was replaced the codes showed a mysterious voltage spike, which was finally traced to the AIT. Nice sluething for you and Jim. My mechanic contends that if I had "left the dammed car well alone" he could've found the problem sooner, but I've gotta have some hobby.

Personally I was hoping it was the ECU, since I just *needed* an excuse to upgrade the programming for yet more boost. Maybe for Father's Day.

opera_house_wk

I have a 92 Explorer that would stall while waiting at stop lights sometimes. It would start to run rough and then violently shake. That would make it run fine again. On the drive home from work every day, there was this high speed right exit turn that the engine would loose power on. Not left turns, just right at about 50 mph. Fooled with this for six months.

What fixed this?

Mr_Shiftright

Oh, man, those are the types of problems that make you want to open a sixpack at 9AM! I can hardly wait to hear!

alcan

Strain on an engine wiring harness connector?

javadoc

I was thinking water in the fuel pump relay? I'm grasping for straws... looking for the unobvious.

/j

Mr_Shiftright

I had a Saab once (thrice actually, I'm done now thank you very much) that had a vane-type fuel pump that often acted up when the car started rolling around. Drove me nuts but it wasn't as definite as just right hand turns. I'd almost have to drive the car to feel HOW it cut out, slowly or rapidly, and this would tell me if it were more likely fuel or electrical.

jlflemmons

in the back somewhere? Maybe getting jarred?

opera_house_wk

Prior to the problem, I noticed I could hear the fuel pump. The car had 140K and I had another car previously that the fuel pump had failed at 160K. Thought I might as well do this now in good weather and not be stuck on the road in the future. I still had fuel pump noise after the new pump was installed and after the problem was fixed. The problem was not electrical.

javadoc

Was it the fuel filter then?

/j

opera_house_wk

I put in an after market pump and that was when I started to experience the problem. Dropping the tank took longer than expected so I didn't put the filter in that day. The next day is when the problem first showed up. A couple of days later I replaced the fuel filter. That seemed to improve things just a little. I thought the after market pump was weak, so a week later I bought a Ford fuel pump and installed it. That make the problem worse. I thought seriously about installing the original pump back in the tank. I never had a problem with the car before I changed the pump.

javadoc

Something was keeping fuel away from the fuel pick-up. Hmmmm, the only time I've replaced a pump as in my Saab 9000T (wasn't fun) and those are down in the tank. So, right turns at moderate Gs starves you of fuel, but at the stoplight too. A pinched line wouldn't do this sporatically, and it wasn't electrical, so the relay wasn't shorting from water.

Did you solve it by just making left turns from now on? lol

My next guess would be (from my Saab experience) that the part that picks up the fuel was installed incorrectly/backwards or something so it wouldn't sip fuel at certain instances.

/j

opera_house_wk

There was no problem in the fuel tank. If the pump had not been replaced, the problem would still have shown up another 20K later.

Unrelated items of interest:

Good guess though. A lot of things can happen in the gas tank out of sight. I had a carberated Ford that the gas pickup tube fell off. It would run out of gas way before empty.

Last summer, on another vehicle, I replaced the fuel pump on an 89 Jeep with 145K. It still pumped fuel but the rail pressure was only 15#. When I unbolted the pump, it fell off the connector hose. Really, it fell off. The hose clamp had never been tightened at the factory. I still wonder if it was just a massive hose leak that caused the low pressure. If I tightened the clamp would it have still worked? Still, it was time for a new pump.

Mr_Shiftright

Those Jeeps have those nasty ribbon filters in the tank don't they. Little bow-tie thingies?

When we're done, I'll tell you about a Jeep problem that took a year to fix.

opera_house_wk

Now this problem didn't happen all the time. I think I adjusted my driving to it. During this period, I took two vacations with the car that were in excess of 2,500 miles each. The care was driveable and I had confidence that it would always get me home. On the last trip, after stopping for lunch, the car stalled in the middle of an intersection with a trailer attached. That was scary! I stuck tiny wires in the fuel pump connector and monitored the voltage. The voltage at the fuel pump would increase indicating a drop in current. Got through that vacation without another incident. Later I installed a DVM multimeter in the passenger compartment connected in place of the fuel pump fuse. Pump current would normally be about 6 amps and when a problem was about to occur, the current would slowly drop down to two amps.

For the longest time I had been chasing what I thought was an electrical problem; bad ground, intermitant connector, relay, cutout switch. This thought was supported by the fuel gauge dropping to zero after a rain when I had a full tank. It started working again before I ever found the cause. Unplugged the tank connector to clean the contacts and for years the gauge problem has never shown up again. Funny how some things can cloud your process of logical analysis. Again, the problem was not electrical. It should have been more obvious to me.

jlflemmons

If the fuel pump is sucking air, the current will drop as there is no load on the pump motor. Could be a leak or hole in the pick-up tube. Sort of like trying to drink a soda through a cracked straw.

opera_house_wk

Now it seems obvious but at the time I thought it was a $50 long shot to buy the pressure regulator. I was so unconvinced, I ground open the old case to inspect the interior. The valve plate is swivel mounted to the diaphragm. This plate seats against the post tube that is connected to the fuel rail. When the valve opens, the valve plate would always tip to the same side. This wore a bevel on the side that almost wore through the tube. This was the result of gravity (because the regulator is mounted on the engine at an angle), the pressure spring not properly centered or both.

When the new pump was installed it was capable of a higher pressure and flow rate. This opened the valve more and allowed the valve plate to slip off to the side. Going to a stop also created a high vacuum that opened the valve even further. When the engine would shake before stalling,the valve plate would re seat itself in the center.

The small G forces of making a fast unbanked right hand turn and the high vacuum of letting my foot off the gas provided the conditions to make the valve stick open. The engine ran lean and lost power.

With the regulator valve open, the pressure was reduced and the motor current dropped. When the valve did not stick, the fuel pressure was normal. I thought these were such a simple device that they never went bad.

ezaircon4jc

It was a vacuum leak. The vacuum hose for the climate control came through the firewall next to the heater hose. The heat from the heater hose "burned" a hole in the vacuum line.

a_l_hubcaps

OK, here's a new puzzle. Note that I stole this from Car Talk; if anyone knows the answer because they heard it on Car Talk, please refrain and let other people figure it out :-) Here goes:

A new model of car goes into production, and as soon as they start delivering them to dealers, the factory begins getting complaints. It seems that exactly two of the cars delivered on each truck will not start on delivery. It is determined that their batteries are dead; after being jumped and driven for awhile to recharge the battery, there are no further problems with the cars. But every time a truckload of these new cars comes into a dealership, exactly two arrive with dead batteries. After receiving a significant number of complaints, the engineers redesign one small part, and the problem goes away. What did they change?

-Andrew L

kik1

have a 93 Chev Lumina van with a 3.8L,
worked perfect until the other day, would not start, not a kick in it, had to tow it to a local shop, they did get it going but they don't know
what they did to make it start. seems to be lots of fuel pressure, but then said anything from fuel pump, crank senso throttle position sensor,
The oil presuure gauge has always been low, they say that could be causing
> the engine to shutdown??? but when it stalls sometimes it starts right up
again,,,sometimes it wont start at all.>
nothing coming up on the codes, now it keeps stalling every once in awhile
while idling it quits.. not real sure , any feedback would be great... I
did put some gasline de icer in just in case. would bad gas, or water in the
gas, cause it to die or , i would think maybe run rough..
> but not stall.... help...
Put coil paks and module on.. ,,,,,,,,,no change,,
Thanks in advance,,,,

Will a tourque convertor solenoid lock up and shutdown a motor , and prevent it from starting??

tboner1965

...but I'll keep quiet a while.

Here is a hint, it involves how the cars sit in the car carrier.

TB

tboner1965

... if the oil pressure sensor detects low pressure.

My mom had a brand new Cavalier over a decade ago that would not start in the driveway because the oil pressure sensor was bad. It would run a few seconds then stall.

Seems the computer was programmed to run a few seconds and if the oil pressure did not come up, it would shut down the engine.

FWIW,

TB

alcan

Are the 2 with the dead batteries the front upper and rear lower on the transporter, and would it have anything to do with the lights on the transporter?

swschrad

I would have said the tie-down chains on two end cars, possibly both nose-down units on the back, just happened to go right across the starter/solenoid assembly and as soon as those sections of the transporter are jacked into road position, you short out the battery positive lead.

I didn't hear the Car Talk answer through tappet noise , so I await the pronouncement of the judges.

shipo

I don't suppose that these cars have alarm systems with a Mercury Switch? Maybe said switch was closing a circuit and causing the battery to drain.

Another possibility would be the battery itself. I heard a couple of years ago that BMW stopped using the conventional “Portable Parking Lot” because many of the cars that were transported in the inclined areas ultimately suffered premature battery failure. All BMW cars are now transported in a truck that holds them level (and covered) for the duration of the trip.

Best Regards,
Shipo