engine not catching at hot start

Tugela

Tugela

Well-known member
May 21, 2007
4,758
563
Seattle
On my new-to-me 98 D1 I've had 2 occasions in the past couple weeks where the truck won't start when the engine is hot. The starter turns, the engine cranks, but it won't catch. It's like it is stalling on startup. I can get it going with a little throttle, then it's fine. Cold starts have been fine 100% of the time so far. Once the engine is running it sounds and performs well.

From searching old threads it sounds like possible culprits are the TPS and fuel pump. I have a complete parts truck so can pull anything I need. The trick is to correctly identify the issue the first time. This is hard since the problem is intermittent: only twice in the month I've owned the truck have I encountered the no hot start problem. No CEL, no codes.

I'm going to start by checking the fuel pressure but if the truck starts fine when cold and runs fine, it doesn't sound like fuel pressure will be an issue.

Anything else I should be looking at?
 
jymmiejamz

jymmiejamz

Well-known member
Dec 5, 2004
6,008
361
35
Los Angeles, Ca
One thing I would look at, which even if this isn't your issue is worth fixing, is the crank sensor wires. If you removed the crank sensor connector, you can pull it up into the engine bay. Then remove the covering on the the harness which will probably reveal that the insulation on the wires has deteriorated. If that is the case, or even if it isn't, I would remove one pin at a time (so you don't mix them up) and put some heat shrink tubing over each wire and then reinstall the pins in the connector.
 
D

discostew

Well-known member
Sep 14, 2010
7,724
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Northern Illinois
Tonybainb said:
change the crank sensor, when they start to fail it is initially on hot starts, cold starts are fine
Click to expand...

I don't know about that. If it was a Bosch unit yes for sure. But just not that common on the old Gems trucks. I think looking at those wires is a good idea and putting shrink wrap on them if they are exposed.

I would be putting a fuel pressure gauge on it and see if it's bleeding down when you shut the truck off. I would look in the vacuum line coming off the fuel pressure regulator to see if that is leaking fuel into the line.

It's easy to check for spark and I would recomend a good spark checker for that. The ones that look like a spark plug and have a clip on them to go to ground are good because they make the system work hard to get accross that gap. If spark can make it thru that thing spark is not your problem.

If you keep taking shit off your parts truck you wont have anything to drive in next years northwest challange or whatever that thing is called. Your going to enjoy the hell out of that when it's not your daily driver getting beat up.
 
pdxrovermech

pdxrovermech

Well-known member
Jul 3, 2009
1,807
57
Portland, OR
I like you so I'll bite. Check fuel pump connections. I often see bad connections at the pump and the plug in the wheel well. they might work well when cold but after getting hot they could be making poor contact. you'll know when you unplug the connection and see it all burnt up.

Now when you say you can get it going with a little throttle, this makes me think its loaded up which could be leaky injectors, MAF, or oxys.

Ckps problem would be an extreme rarity on a GEMS system.

No codes?
 
Icannap1

Icannap1

Well-known member
Mar 3, 2015
123
21
OC, CA
I have a 97 d1 with a gems 4.0 motor and I am having the same problem if I drive it then turn it off do the same start it, drive it, shut it off, then attempt to start it up again it will start and immediately stall unless I pump the gas and rev the throttle for about a minute or so till it clears up and idles. I can then drive it where ever I want to go but once I turn it off I need to repeat the cycle when the engine is at running temperature. I replaced the fuel rails Schraeder valve and installed a fuel pressure gauge in its place. My fuel pressure gauge running is around 38 prior to start just after turning the key before crank it is at 40. I have noticed after 3 hours it will drop to 20, after 8 hours it will be down to 10, and of course by the next morning it will be at 0 after the truck has been turned off. My guess is a sensor as others have said but no codes once a p1316 I believe. There has to be a better way than just throw parts at it.
 
Tugela

Tugela

Well-known member
May 21, 2007
4,758
563
Seattle
pdxrovermech said:
No codes?
Click to expand...

Correct. No codes. I haven't done anything to try to diagnose the problem since the first post as I've been pretty busy, but I've been driving the truck and in the last week there has been no return of the problem. Thanks for the suggestions, this is a good list of places to start looking.
 
9

97GreenMeanie

Well-known member
Mar 24, 2014
48
0
ny
Icannap1 said:
I have a 97 d1 with a gems 4.0 motor and I am having the same problem if I drive it then turn it off do the same start it, drive it, shut it off, then attempt to start it up again it will start and immediately stall unless I pump the gas and rev the throttle for about a minute or so till it clears up and idles. I can then drive it where ever I want to go but once I turn it off I need to repeat the cycle when the engine is at running temperature. I replaced the fuel rails Schraeder valve and installed a fuel pressure gauge in its place. My fuel pressure gauge running is around 38 prior to start just after turning the key before crank it is at 40. I have noticed after 3 hours it will drop to 20, after 8 hours it will be down to 10, and of course by the next morning it will be at 0 after the truck has been turned off. My guess is a sensor as others have said but no codes once a p1316 I believe. There has to be a better way than just throw parts at it.
Click to expand...

I've had the exact same issues as you on my 97.
And when it does finally start up, it ran rough and a bit of unburnt fuel in black smoke comes out until it clears itself up.
It only happens when I've been driving for a while, shut it off, then try to start it up again.

I haven't thrown any parts at it yet.
 
Icannap1

Icannap1

Well-known member
Mar 3, 2015
123
21
OC, CA
Newly rebuillt BA engine so it has new o rings and gaskets. It has new plugs and wires everything else is original sensors, injectors, maf sensor, and so on. Starts great when cold but after it has been running and turned off then restarted 5-10 after it has the problem but of course after reving it for a minute or so it clears up. I even disconnected the fuel temp sensor on the fuel rail as I noticed when it is cold the resistance is high in the kilo ohms when hot it's below an ohm. So with the sensor disconnected it would think it is cold but that made no difference to the issue. Problem still exists. I want to obtain a good good crank position sensor I read that when they are going out and they are hot from operation that it may be failing. My question on that is if the crank position sensor was failing I would think that the engine would backfire but that has not happened.

A few times maybe 3 times in the year that I have driven it has lost power for a brief 5 seconds while driving and a fowl smell from the exhaust would be present. I would let go of the gas pedal for 5 seconds and then power would return it is good as if nothing happened and no code.

What do you think is the problem a engine phantom or gremlin and how else would you do to troubleshoot that?

Any help would be greatly appreciated.
 
D

discostew

Well-known member
Sep 14, 2010
7,724
1,018
Northern Illinois
Icannap1 said:
Newly rebuillt BA engine so it has new o rings and gaskets. It has new plugs and wires everything else is original sensors, injectors, maf sensor, and so on. Starts great when cold but after it has been running and turned off then restarted 5-10 after it has the problem but of course after reving it for a minute or so it clears up. I even disconnected the fuel temp sensor on the fuel rail as I noticed when it is cold the resistance is high in the kilo ohms when hot it's below an ohm. So with the sensor disconnected it would think it is cold but that made no difference to the issue. Problem still exists. I want to obtain a good good crank position sensor I read that when they are going out and they are hot from operation that it may be failing. My question on that is if the crank position sensor was failing I would think that the engine would backfire but that has not happened.

A few times maybe 3 times in the year that I have driven it has lost power for a brief 5 seconds while driving and a fowl smell from the exhaust would be present. I would let go of the gas pedal for 5 seconds and then power would return it is good as if nothing happened and no code.

What do you think is the problem a engine phantom or gremlin and how else would you do to troubleshoot that?

Any help would be greatly appreciated.
Click to expand...

One thing you guys gotta get passed is that just cause it's NEW and just REBUILT doesn't mean something didn't get messed up. If your not going to check shit these guys are telling you they have seen cause a problem just cause it's new then you might never fix this bitch. I've been fixing cars for 35 yrs boys. I'll always recheck my work, I fuck shit up sometimes.

Put a fuel pressure gauge on it and try to duplicate the problem. These trucks sound fuel related to me. If you don't have a gauge, get one. I would keep a scanner on it till you figure it out. Start by watching TPS and your O2 sensors. When it acts up hopefully you will catch it. Figure out how you drove it when it acted up and keep driving it like that to try to make it happen.
 
Tugela

Tugela

Well-known member
May 21, 2007
4,758
563
Seattle
Following up on this thread so future researchers learn the conclusion. New fuel pump resolved the issue.
 
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