hard starting when motor cold/ been sitting for a while

B

bondmansmark

Registered
I own a 93 markviii. The car cranks fine just takes a while/multiple tries to start. Only does it on cold startups, never when at operating temp or when just recently turned off. Also found that when I cycle the key on/off multiple times before I start/cold start it usually starts a lot faster.
Leaking fuel pressure?
cam sensors?

All my regular maintenance items are up to par.

Open to suggestions.:eek:
 
RE: hard starting when motor cold/ been sitting for a while

Sorry forgot to mention I R@R fuel pump with 255 walbro a couple months ago. maybe its related. Id like to put a fuel pressure gauge on the shrader valve before I lower the tank again.
what do you think ? Is there an other way of checking fuel pressure?
Would a faulty cam sensor produce the same results?
I think I had a code for one of the cam sensors a while back,could that be related if so that' next on my list.

let me know.
 
RE: hard starting when motor cold/ been sitting for a while

Your description sounds like fuel pressure leaking back. Another possibility could be the fuel pressure regulator.

You can get a fuel pressure diagnostic guage that will screw right onto the schrader valve on the fuel rail. Or you can go to Steeda dot com and get what I have.

http://mark8.org/users/driller/pics/AFPR3.JPG

The guage has a 1/8" male pipe thread. To temporarily mount this on the rail, you could use the included adapter or you can remove the schrader valve and replace with a 1/16" male pipe X 1/8" female pipe adapter like I did for a permanent mount.
 
RE: hard starting when motor cold/ been sitting for a while

Thanks for the specifics on the fuel pressure guage/adapters.
Ill try that and R@R both cam sensors just for kicks.
How can one diagnose the fuel pressure regulator?
Should I upgrade to an aftermarket regulator? I do have the 255 Walbro.
Is it nessesary?

Also noticed today on cold startup that it started on the fourth
crank/all small cranks. I think it always starts on the fourth crank now that I think about it.::wtf::
 
RE: hard starting when motor cold/ been sitting for a while

[div class="dcquote"][strong]Quote[/strong]
...How can one diagnose the fuel pressure regulator?[/div]

From the manual...

A11 FUEL PRESSURE REGULATOR CHECK


~ Disconnect return line at fuel pressure regulator. Connect outlet of regulator to appropriate receptacle to catch return fuel.

~ Run fuel pump as in Test A2.

~ Is fuel pressure within specification limits for this engine?

Yes
GO to «A18».

No
REPLACE fuel pressure regulator. RECHECK pressure, GO to «A3».

A12 FUEL PRESSURE REGULATOR CHECK


~ Disconnect return line at fuel pressure regulator. Connect outlet of regulator to appropriate receptacle to catch return fuel.

~ Run fuel pump as in Test A2.

~ Is fuel being returned to the regulator with low pressure in system?

Yes
REPLACE regulator. RECHECK pressure, GO to «A3».

No
GO to «A4».

A13 FUEL PRESSURE REGULATOR LEAK TEST


~ Disconnect return line at fuel pressure regulator. Connect outlet of regulator to appropriate receptacle to catch return fuel.

~ Run fuel pump as in Test A2.

~ Turn off fuel pump by removing ground or turning ignition to OFF position.

~ Observe fuel return flow from regulator and system when pump is off.

~ Remove vacuum hose from fuel pressure regulator and check for presence of fuel in regulator fitting (diaphragm leak).

~ Is there return flow when pump is turned off and system pressure is dropping or is there fuel in regulator fitting?

Yes
REPLACE regulator and RECHECK pressure, GO to «A3» and «A4».
If OK, GO to «A5». If not OK, REPEAT A3 and follow procedure.

No
If leakdown concern exists, GO to «A8». Otherwise, GO to «A7».
 
RE: hard starting when motor cold/ been sitting for a while

[div class="dcquote"][strong]Quote[/strong]
I think it always starts on the fourth crank now that I think about it
[/div]
That sounds like the CAM sensor.
When the cam sensor fails the computer will take a "guess" at the which cylinder is in the firing position.
I think after 4 guesses it's covered all it's options.. if I remember correctly.

The cam sensor info is for firing the injectors, and the crank sensor is for firing the ignition.

Cam sensor is an EASY fix...
remove the power steering resevior and coil pack on the driver side of the motor.. and the cam sensor is right behind the Powersteering resevoir, the sensor is held in place with one bolt

Tiffany changed hers in a Oreilley's Auto Parts Parking lot.

..easy smeasy compared to dropping the tank!!
 
RE: hard starting when motor cold/ been sitting for a while

[div class="dcquote"][strong]Quote[/strong]
...When the cam sensor fails the computer will take a "guess" at the which cylinder is in the firing position.I think after 4 guesses it's covered all it's options..
[/div]

Interesting. THIS is why I wish I knew more about the inner workings of the EEC.

I agree that it 'guesses' which injector to fire, but if it 'guesses' when the cam sensor fails, and after 4 'guesses' it has covered all it's options, why does it always start on the fourth crank? Are the first three 'guesses' always wrong and the fourth 'guess' always right? ::roll::
 
RE: hard starting when motor cold/ been sitting for a while

Just tackled the camshaft sensor. Twelve dollars and 20 min. later
it's done. Well almost done, have to go back in and replace/crimp new wires going into the sensor. The wires were in horrible shape/partially melted. Im assuming from contact with the engine.
The wires were exposed/ no elec. tape and someone did a poor job of crimping the wires right/bare wire sticking out and possibly making contact. Also there is an extra bare wire/no plastic on wire, coming from exactly the same place as the two wires that go to to sensor. Im gussing this bare wire belongs to one of the two others and was overlooked when they crimped the wires. I balled up the mystery wire and wrapped it up in electrical tape until I figure out if in fact it should of been crimped with one of the other two.
At least now I know that the camshaft sensor has been worked on in the past.

Sorry for the long post. Oh and make sure you inspect the wires and not just replace the sensor like I did.

Also thanks for the info on testing the regulator thats next after these sensos.

Any ideas on the wires? Theres only supposed to be two right?::wtf::
 
RE: hard starting when motor cold/ been sitting for a while

it may have been a bad connection rather than the sensor itself...
But.. for 12.00, why not replace it with a new one.

I cant remember how many wires went to it, without removing my PS res. I cant tell.

I "THINK" there were only two, but I may be mistaken.
 
RE: hard starting when motor cold/ been sitting for a while

Thank you driller.
The wire was wound up in a "shield" type material. It was grey/aluminum looking. Like some kind of insulation. It would easily
break when touched/like when something is dry rotted.

Should I ground it?
the wire itself is about 3.5- 4 inches in lenght.
Is there any known areas around where it could've been grounded to?

I can take pics just have no idea how to post.
 
RE: hard starting when motor cold/ been sitting for a while

Universally, the grounded shield is almost always grounded at the end opposite the sensor from what I have seen. The shield is to prevent RF(Radio Frequency) interference and is not integral to the actual function unless its failure allows RF interference to degrade the signal.

You can easily attach pics direct from your PC to your message(post). It must conform to size limitations. When composing a message, scroll down below and click "Click here to choose your attachments" and follow the prompts. Browse for the file on your PC and select the pic file to open. Check the corresponding button for the type of file, then to have the pic actually 'show up' with the message, be sure to checkmark the appropriate box on the attachment. Lastly click "Upload File" button. You can repeat twice more to attach up to three pics per post.
 
RE: hard starting when motor cold/ been sitting for a while

I had the cam sensor problem. I called the dealer, asked to speak to a tech (it actually worked at the third or fourth dealer i called) and he said that it's probably not the sensor but the wires. So i hacked the wires directly to the sensor (no connector) and my problem was gone. This was before i found LOD.
 
RE: hard starting when motor cold/ been sitting for a while

[div class="dcquote"][strong]Quote[/strong]
he said that it's probably not the sensor but the wires. So i hacked the wires directly to the sensor (no connector) and my problem was gone. This was before i found LOD.
[/div]

Good point!
 
RE: hard starting when motor cold/ been sitting for a while

Sorry about the size, this is my first pic post ever.
Will try to make smaller in the future.

Looks like a third wire to me.

What do you think?
 
RE: hard starting when motor cold/ been sitting for a while

I suppose anything's possible. Someone could've replaced the sensor once and just twisted the wires together and you're seeing the tail?!

I would peel 'er back in the harness and investigate further. If it's the shield it will become obvious in an inch or two.
 
You must log in or register to reply here.
Back
Top