Is this a Jeep thing?

[Nathanael Rusciolelli]

A couple months ago I installed the fuel injector heat shield on my '99 to try and fix some hard starting issues. Those didn't work, so I recently installed a new bosch fuel pump because when I tested the fuel pressure, it was very low. The new pump seemed to fix the issue for about a week and once again, it is having the same problem (hard starting when hot). Is it just one of those Jeep things? I was thinking about new fuel injectors but something tells me that wouldn't help.

 

[Jerry Bransford]

It's definitely not a Jeep thing, mine starts up fine when it's hot or cold. I wish I had a suggestion for you though, you've already done the same two things I would have done first for that issue. My next step would be to Google that issue.

 

[Chris]

The hard starting when hot is a notorious issue with the 4.0 engines.

My Cherokee did this and my TJ did as well. The issue is heat soak on the fuel injectors. Hell, I believe there was an official TSB about this from Jeep.

 

[Chris]

BTW, when it's hot and has trouble starting, try this and see if it works.

Turn the vehicle off. Turn the ignition to the on position (not the engine on, just the accessories so the fuel pump can prime). Do that 3-4 times, letting the fuel pump prime for 3-4 seconds each time before turning it off.

Then, start the engine up and see if it starts right up without hesitation.

 

[Nathanael Rusciolelli]

The hard starting when hot is a notorious issue with the 4.0 engines.

My Cherokee did this and my TJ did as well. The issue is heat soak on the fuel injectors. Hell, I believe there was an official TSB about this from Jeep.

What do you guys think of an injector upgrade? I've been reading on the web and it seems it really works for some people, while others have no success.

 

[Nathanael Rusciolelli]

BTW, when it's hot and has trouble starting, try this and see if it works.

Turn the vehicle off. Turn the ignition to the on position (not the engine on, just the accessories so the fuel pump can prime). Do that 3-4 times, letting the fuel pump prime for 3-4 seconds each time before turning it off.

Then, start the engine up and see if it starts right up without hesitation.

I've performed this test numerous times with no dramatic results.

 

[Chris]

What do you guys think of an injector upgrade? I've been reading on the web and it seems it really works for some people, while others have no success.

I did it to my XJ and noticed no difference at all. I think it's nothing more than a placebo effect.

If your injectors aren't bad, I wouldn't waste the money personally.

I've performed this test numerous times with no dramatic results.

Interesting, on my XJ it made all the difference in the world.

 

[jeepXcore]

Dunno if this is an option/solution for a Jeep, but I know heatsoak is an issue with VW GTI's because of the turbochargers during hot days, our solution was upgrading to a front-mount intercooler. Are there aftermarket intercoolers available for TJs?

 

[Chris]

Dunno if this is an option/solution for a Jeep, but I know heatsoak is an issue with VW GTI's because of the turbochargers during hot days, our solution was upgrading to a front-mount intercooler. Are there aftermarket intercoolers available for TJs?

Why would you need an intercooler for a TJ? They don't use forced induction.

 

[jeepXcore]

Why would you need an intercooler for a TJ? They don't use forced induction.

lol, yeah, that's what I wasn't sure about, I'm really only familiar with boosted engines, wasn't sure if more cool air would help with the n/a engines.

 

[Jerry Bransford]

What do you guys think of an injector upgrade? I've been reading on the web and it seems it really works for some people, while others have no success.

Waste of $$$. Those who claimed it worked for them are usually just willing victims of the Placebo Effect.

 

[Jerry Bransford]

BTW, when it's hot and has trouble starting, try this and see if it works.

Turn the vehicle off. Turn the ignition to the on position (not the engine on, just the accessories so the fuel pump can prime). Do that 3-4 times, letting the fuel pump prime for 3-4 seconds each time before turning it off.

Then, start the engine up and see if it starts right up without hesitation.

That problem you're checking and that cycling the ignition switch 3-4 times for has nothing to do with a hot engine, that type of problem occurs when the engine has been sitting a while, usually overnight, and a leaky check valve in the fuel pump assembly allowed the fuel to drain out of the engine and all the way back down to the gas tank. The issue that can be temporarily worked around by cycling the ignition switch has nothing to do with a hot engine/heat soak.

Heat soak is usually caused by heat rising up from the engine and causing the fuel inside the fuel injectors to vaporize/evaporate. Insulating them from the engine heat can often help if not cure it. The middle injectors are the most vulnerable, one TSB (tech service bulletin) advises to wrap the #3 fuel injector with insulation and zip-tie it in place. Laying insulation under the injectors in the little indentations under them can help too.

 

[Chris]

That problem you're checking and that cycling the ignition switch 3-4 times for has nothing to do with a hot engine, that type of problem occurs when the engine has been sitting a while, usually overnight, and a leaky check valve in the fuel pump assembly allowed the fuel to drain out of the engine and all the way back down to the gas tank. The issue that can be temporarily worked around by cycling the ignition switch has nothing to do with a hot engine/heat soak.

Heat soak is usually caused by heat rising up from the engine and causing the fuel inside the fuel injectors to vaporize/evaporate. Insulating them from the engine heat can often help if not cure it. The middle injectors are the most vulnerable, one TSB (tech service bulletin) advises to wrap the #3 fuel injector with insulation and zip-tie it in place. Laying insulation under the injectors in the little indentations under them can help too.

Ahhh, that makes sense. On my XJ though, it would happen (for whatever reason) when I would start the car when it was hot (as in I only let it cool down for 5 minutes or so, then got back in and started it up).

Cycling the ignition 3-4 times always alleviated the issue oddly enough.

 

[Jerry Bransford]

Ahhh, that makes sense. On my XJ though, it would happen (for whatever reason) when I would start the car when it was hot (as in I only let it cool down for 5 minutes or so, then got back in and started it up).

Cycling the ignition 3-4 times always alleviated the issue oddly enough.

Cranking it in the Start position is what probably got yours started. That allowed the likely vaporized fuel to get pumped out of the fuel injectors and then be refilled by 'good' fuel by the injectors being energized during the cranking process. The injectors don't try to spray/open/close when you just cycle the ignition on-off-on and thus the fuel pump.

 

[Nathanael Rusciolelli]

I've been starting to experiment with using the gas pedal while starting the engine. It does seem to start a little faster with the accelerator pushed almost to the floor. It's not like it makes it start immediately, it just seems to help a little.

 

[DC0046]

I remember almost 45 years ago I worked for a local VW dealer. One of my duties was picking up and taking home customers who were having their vehicles serviced at the dealership. I used a new VW Van (wish I had one now). Invariably, the van would end up vapor locking in the middle of the trips with the van full of customers. More than once I found myself crawling under the van with a coke bottle full of cold water pouring it in fuel lines. It usually worked, but didnt breed any confidence for those in the van who owned VWs. Don't mean to hijack the thread, but a similar issue I remember from a long time ago with a different vehicle.

 

[Mike_H]

So, like Jerry is saying, if the fuel is vaporizing in the injector, the only way to combat the problem is reduce underhood temperature (or otherwise insulate the injector from the heat). Some of those louvers may help, even if they look dumb. I know in the boating world, people have problems with vapor lock due to the Hot engine heat soaking the carb or injectors, and taking a long time to start (if at all). In almost every instance, running the blower fan or popping the engine cover solves the issue. Ethanol fuel is also a contributor...Alchohol vaporize easier than gasoline, so less heat is required to cause hot starting issues.

 

[Jerry Bransford]

I've been starting to experiment with using the gas pedal while starting the engine. It does seem to start a little faster with the accelerator pushed almost to the floor. It's not like it makes it start immediately, it just seems to help a little.

Opening or pumping the gas pedal on a fuel injected engine with a throttle body does absolutely nothing other than opening and closing the throttle valve plate. Doing so doesn't pump more or actually any fuel into the engine like happens with older carbureted engines. It will start in the same length of time leaving the gas pedal untouched. You'd have the same amount of fuel in the combustion chambers when the engine finally fires if you pumped the gas pedal 100X or if your foot never touched the gas pedal.

 

[Nathanael Rusciolelli]

Opening or pumping the gas pedal on a fuel injected engine with a throttle body does absolutely nothing other than opening and closing the throttle valve plate. Doing so doesn't pump more or actually any fuel into the engine like happens with older carbureted engines. It will start in the same length of time leaving the gas pedal untouched. You'd have the same amount of fuel in the combustion chambers when the engine finally fires if you pumped the gas pedal 100X or if your foot never touched the gas pedal.

I wasn't sure if I was doing anything or not. I figured with the throttle valve open, it would increase airflow and maybe help start it up.

 

[94c2500]

A couple months ago I installed the fuel injector heat shield on my '99 to try and fix some hard starting issues. Those didn't work, so I recently installed a new bosch fuel pump because when I tested the fuel pressure, it was very low. The new pump seemed to fix the issue for about a week and once again, it is having the same problem (hard starting when hot). Is it just one of those Jeep things? I was thinking about new fuel injectors but something tells me that wouldn't help.

I'm assuming you already replaced the foil heat shield that fits under the fuel rail?
Those are cheap insurance against heat soak and cost around $4.00 average.
Photo of heat shield : https://www.partsecatalog.com/chrysler-cbxcb060

You can also insulate each individual injector by using spark plug boot/wire insulators.
They come in various styles and would need to be trimmed for length. It might require you pull your fuel rail in order to slip them on, or you could split them and wrap around and secure. You could even split several lengthwise and wrap around your fuel rail itself for a little extra insulating effect.
I've included a link and photo to one that Autozone sells, and the same brand has other part numbers listed on Autozone's site.

Autozone Thermo Tec Spark Plug Tube Insulator

Part #14200

http://www.autozone.com/ignition/sp...silver-spark-plug-wire-heat-shield/398830_0_0

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A link to a YouTube video showing someone experiencing similar heat soak and what they did: