Jump to content

3.4 DOHC hot starting problem


BN

Recommended Posts

93 CS. I drove the car when it was really hot out and when I made short stops at stores the car did not want to start again without pumping the gas. Once started it ran fine. Also started fine when cold?

Link to comment
Share on other sites

He did replace his coils not too long ago with new ones. I know the temperature has been in the 90s the past couple days. I'm leaning towards heat soaked starter.

Link to comment
Share on other sites

What the hell does a heat soaked starter have to do with starting after pumping the gas?

 

Forgot that small point!

 

 

Anywho, when I had this similar issue, I had to replace the ICM.

Link to comment
Share on other sites

Ignition module can be tested an O'reilly/Autozone. Take if off when engine is hot (at least as warm as you can still get it off) and run down and have them test it a few times. I'm guessing though that ICM isn't your problem or it would be failing more often that just when starting. Also check fuel pressure hot. Should be ~43psi and make sure it doesn't start bleeding off after you shut it off. My father dropped off my sister's MC Z34 at my place last night because it also won't start after a hot soak. Checked it tonight and there is only 28-32psi. I still need to check out if it has either has a bad regulator or dying pump. I think it's going to be the pump even though it's not very old. It doesn't sound healthy.

Edited by jman093
Link to comment
Share on other sites

I also am having a start problem that maybe similar/different; my car (3.4 olds cutlass convertible) will cold start and run fine... However, when I shut the car off at operating temperature it will turn over kinda fast but it will idle up and down (500 to 1500 rpms) and die. It will do this repeatly unless I either put my foot on the gas to stablize it or it put it gear immediately which in turn will and will shut off... I have cleaned the IAC (had the fuel injectors checked and a bounty of other work done for unrelated problems)

 

The car has a new ICM, coils, wires, plugs, intake manifold gaskets, new mass airflow sensor, and all electrical connections have been sealed up. No check engine or service engine light comes on. Still the problem persists... This may sound crazy but I wonder if it has anything to do with throttle position sensor? air condition being on? suggestions anyone please...

 

Oh and another thing I have noticed is that at lower speeds/rpms the car has a slight buck/shutter that is nearly undetectable...

Link to comment
Share on other sites

Original Poster:

It's been very hot recently....you may be suffering from vapor lock, the fuel is boiling in the rail. You try to start the engine hot and it will not fire properly.

Edited by 55trucker
Link to comment
Share on other sites

Hmmm. It's 118 here in Phoenix and so far the only problem I had with starting my 3.4 is when I filled it up with good gas and parked it inclined. Otherwise, I have driven it, stopped multiple times without problems. I, too is wondering what it is....

Link to comment
Share on other sites

Original Poster:

It's been very hot recently....you may be suffering from vapor lock, the fuel is boiling in the rail. You try to start the engine hot and it will not fire properly.

Now that it's not as hot it doesn't seem to be doing it as much. I took it to a shop and they must have started it close to a hundred times over several hours and it started fine, so you could be right about the vapor lock. is there anything that can be done about vapor lock?

Link to comment
Share on other sites

Well, as stated perhaps you need to have the fuel pressure checked.

The fuel shouldn't be boiling in a fuel injected environment, the pressure should keep it from doing that.

But then, that doesn't mean it can't happen, I get this situation in my Dodge Shadow, if when driving in hot very weather with the A/C running, the fuel will vapor lock in the rail and the engine goes flat & missees. Shut the car down, let it cool off and presto! it runs again as it should do.

One thing I have done to keep under hood temps down is to wrap the front manifold & crossover with header wrap. I'm amazed how much cooler the thermostat housing/rad return hose & the fuel lines are just because there is not the radiant heat coming off the crossover pipe that cooks them, not to mention everything else that is close by.

 

Picture001Large.jpg

Edited by 55trucker
Link to comment
Share on other sites

the stuff u wrapped on the crossover/header exhausted. What is it called? Header wrap? I think I am going do the same on my car, motor is out, I am going to do it as well. Hard to do wrap job?

 

Well, as stated perhaps you need to have the fuel pressure checked.

The fuel shouldn't be boiling in a fuel injected environment, the pressure should keep it from doing that.

But then, that doesn't mean it can't happen, I get this situation in my Dodge Shadow, if when driving in hot very weather with the A/C running, the fuel will vapor lock in the rail and the engine goes flat & missees. Shut the car down, let it cool off and presto! it runs again as it should do.

One thing I have done to keep under hood temps down is to wrap the front manifold & crossover with header wrap. I'm amazed how much cooler the thermostat housing/rad return hose & the fuel lines are just because there is not the radiant heat coming off the crossover pipe that cooks them, not to mention everything else that is close by.

 

Picture001Large.jpg

Link to comment
Share on other sites

the stuff u wrapped on the crossover/header exhausted. What is it called? Header wrap? I think I am going do the same on my car, motor is out, I am going to do it as well. Hard to do wrap job?

 

This wasn't difficult at all. I had the crossover & the front manifold off seeing as I had to get at the ICM. I just clamped them into a bench vise and then started wrapping the header wrap all around them.

The wrap itself is 2" basic non treated. It's good to approx 1000 degrees. I picked it up on ebay. It was very reasonably priced even with the shipping to Ontario.

Here is a link to the seller who sent it to me. His name is James & he was very accommodating.

 

http://cgi.ebay.com/ebaymotors/Exhaust-Wrap-2-x-50-BLACK-Header-Thermal-Insulation-_W0QQcmdZViewItemQQhashZitem2eb6e74d00QQitemZ200637107456QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Edited by 55trucker
Link to comment
Share on other sites

I just had my motor rebuilt and never thought to have this done while it was out. Smart idea, it really cooks in there. When I changed the fuel filter the fuel that had sat in the lines up in the engine compartment ran back so hot it made the lines hard to touch and almost caused burns. We were concerned that the car was shorting out through the fuel line (and therefore ready to run lest a fire start) until we realized the supernova hot engine compartment was to blame.

 

Ok, I am exaggerating the engine temp a bit, but I am wondering about how much my fans are actually running. Need to check that.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...