A Possible and Minor Vapor-Lock Cause with My Old Trooper

BonzaiDuck

Lifer
Jun 30, 2004
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Yes, you have known for about five or six years that I am obsessed with this old, orphaned '95 SUV.

And people who are OCD about their vehicles may take some little thing, expand it in their imagination and worry or fret about it without end!

Couple weeks ago, I took her in to my Solid Gold repair shop, having laid the groundwork for the visit over more than a year. First, I wanted to replace the gas-tank sending unit that informs the needle gauge and an idiot light ("tank-empty") on my instrument-panel/dashboard. I found the original part brand-new in ISUZU carton through the US ISUZU parts depot, who found it in a warehouse in Japan. For $135, I had to wait three months, but I got it. I planned with the service advisor, who provided an estimate, to do it this spring.

And before I took it in for the work, I thought I noticed a "hard-starting" situation to which I'd not paid attention before. Since the sensor replacement meant removing the gas-tank, and a new fuel-pump ($150) required the same thing, we all decided the Trooper deserved it after 200,000 miles.

The car was returned to me. The idiot light was behaving properly. And the vehicle ran like new. [It just occurred to me I posted another thread about this, so I apologize]. BUT -- ANYWAY!

The owner and service advisor both affirmed that the Trooper "just starts right up -- no problem". The car had been sitting for a few hours when I went to pick it up, and they seemed absolutely spot-on -- "It starts right up!" Now, later on, I discovered that this was always the case when the engine was cold. Further, if I returned home, turned the car off in the garage, waited FIVE MINUTES or so and then turned the key again -- it started right up! Great! Now I've discovered that if you let the car sit for 20 minutes to an hour or so, the starter would crank for about 10 seconds -- maybe more -- if you tried to start it.

Pumping the gas or hitting the accelerator once or twice before turning the key seemed to reduce that time.

It seems to be a vapor-lock situation. Just after the car has been driven, some part of the fuel line is still cool from the car's movement. After it sits, there is no draft from the fan, no air coming through the radiator -- and it heats up before it cools off.

This may have been a condition for the entire time I've owned the car -- I can't be sure. But what can be done about it? Should I try and insulate gas hoses or lines running to the engine? I discovered today that putting a fan on the engine after putting the car in the garage eliminates this starting delay if I come back and turn the key in less than an hour.
 

RLGL

Platinum Member
Jan 8, 2013
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I cold, it's not vapor lock. Is this beast fuel-injected? If so do a key on fuel pressure test.
 

BonzaiDuck

Lifer
Jun 30, 2004
15,740
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I cold, it's not vapor lock. Is this beast fuel-injected? If so do a key on fuel pressure test.
Yes -- fuel injection. What do you mean by "I cold, it's not vapor lock . . . "?

I suppose that I'm keen on this matter of the starter turning over too long when the engine is still hot after sitting more than 10 minutes -- I just replaced the starter motor last year, so I don't want to increase wear and tear on it.

At the time my shop replaced the tank sensor and fuel-pump, they did a fuel pressure test. Are you saying to do the pressure test with the key on?

I'll keep an eye on this thread for now. I've got the driving fever. I need to buy some half-and-half for the sunday coffee. So I'm going to run it out today. Maybe visit the truck-farm canopy for some vegetables -- anything! Drop by Carl's Jr for a chicken sandwich. The Trooper's Manitou beckons like a dog who wants to go for a walk . . .
 
Last edited:

Torn Mind

Lifer
Nov 25, 2012
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Do you mean the thing does not start easily when hot?

Your fuel injector seals might have failed and liquid gas is being dumped into a cylinder....
 

Toastedlightly

Diamond Member
Aug 7, 2004
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I had a similar issue on an 89 Trooper (it had the cylinder though). The symptoms are almost the exact same. The diaphragm in my fuel pressure regulator had ruptured allowing fuel to pour into the vacuum system and into the engine. This can easily be tested if you take the vacuum hose off the fuel pressure regulator. If fuel comes out of the regulator that could be it.

The second one I could see if is if the engine temp sensor is bad. It may be giving the engine the signal it is cold and thus it starts well cold but refuses to restart. On my older Fords the ECU used a separate probe from the one used for the gauge (unsure about the trooper).
 
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Torn Mind

Lifer
Nov 25, 2012
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I had a similar issue on an 89 Trooper (it had the cylinder though). The symptoms are almost the exact same. The diaphragm in my fuel pressure regulator had ruptured allowing fuel to pour into the vacuum system and into the engine. This can easily be tested if you take the vacuum hose off the fuel pressure regulator. If fuel comes out of the regulator that could be it.

The second one I could see if is if the engine temp sensor is bad. It may be giving the engine the signal it is cold and thus it starts well cold but refuses to restart. On my older Fords the ECU used a separate probe from the one used for the gauge (unsure about the trooper).
Some good advice when testing fuel pressure regulator in this vid.
 

BonzaiDuck

Lifer
Jun 30, 2004
15,740
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TornMind, PCGeek and ToastedLightly have some useful ideas which I will explore.

Hans! That's what my dentist told me when I mentioned that my rental property was being listed for sale! "You've likely got 14 years left to live. Spend the money! Buy a new car!"

I bought the SUV in 2002 -- six or seven years old. I started an Excel spreadsheet immediately -- with DATE, MILEAGE, DESCRIPTION and EXPENSE columns. A person might look at the history and ask "why didn't you get rid of it when . . . ?" But it shows that I've spent $100/month (average) since I bought it, including the purchase price in the items averaged. Ideally, it cost less if I subtract the repairs made for my own negligence or a repair shop's choice of defective parts.

The engine is simply going to "keep on going" until it somehow dies. It doesn't pollute; it doesn't leak; it doesn't burn oil. The transmission has relatively fresh fluid in it, and shows no signs of needing service since I replaced the original in 2004.

So -- today is Friday, heading toward COB/close-of-business. I"m going to run it by the repair shop next week with the list of ideas for possible causes. They'll find the trouble, and they'll fix it.

It seems that the problem -- accepting the ideas of a cause -- is pretty minor. It isn't that I cannot start the car when it is warm. I need to pump the gas once and turn the key, at which time it may turn over with some noticeable delay.

The problem with buying a new car -- excluding all of my financial strategies to spite late-life circumstances -- is the hassle of looking for a vehicle, selecting a vehicle, negotiating, and the learning-curve on new technology. That is, these hassles, weighed against repair episodes for an old car. But mainly, if I only drive 4,000 miles per year, the Trooper otherwise runs great to original specs, and it doesn't cost me much --- I can't see that sinking $50,000 into a new car which will only be driven 4,000 miles/annum -- I can't see that it is worth it. It doesn't make sense.

Instead, if I can get 5% return on $200,000 for three years, buying a new car may seem painless, but it doesn't make much more sense. They only reason it would make immediate and emergent sense arises when the Trooper has truly, entirely, completely died. Or it gets totaled in an accident -- which seems more likely even as accidents should be unlikely.
 
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BonzaiDuck

Lifer
Jun 30, 2004
15,740
1,469
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I had a similar issue on an 89 Trooper (it had the cylinder though). The symptoms are almost the exact same. The diaphragm in my fuel pressure regulator had ruptured allowing fuel to pour into the vacuum system and into the engine. This can easily be tested if you take the vacuum hose off the fuel pressure regulator. If fuel comes out of the regulator that could be it.

The second one I could see if is if the engine temp sensor is bad. It may be giving the engine the signal it is cold and thus it starts well cold but refuses to restart. On my older Fords the ECU used a separate probe from the one used for the gauge (unsure about the trooper).
Before either testing it myself or having my shop do it, I think there's a good chance above all that the fuel pressure regulator -- "the fuel injection pressure regulator" or "fuel pressure control valve" -- is the culprit. That's a $50 part. But I think this was an item where ease-of-repair drives the bottom-line: I think one must remove the entire "common chamber" or intake manifold to allow removal of this part. I believe I asked someone to do it two or three years ago, and they discovered the removal problem.

That I decided to try and replace it was not based on testing, but it was an item that was cheap and I just had it in mind to make the replacement. The shop manual only speaks to diagnostics -- it shows the position and shape of the regulator/valve, but there are no enumerated steps for its removal.

Thanks for your input, based as it was in firsthand experience. And of course, since they can test the valve, if it's the temperature sensor it might not be so troublesome.