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Discussion Starter · #1 ·
Hi everyone, it has been some time from my last post, but I'm back. From several weeks I drive my Tahoe much more and I've discovered a problem with it. It has a trouble with starting when the engine is hot, but not immediately after shutting it down. So I can shut it down for a while and start with no problem, but after 30 - 60 minutes of staying I have to crank longer or it doesn't even start. I remember noticing twice or maybe three times that after starting hot and driving some seconds, RPM's were waving for a short while. I assume that there is a leak on a fuel line and it sucks some air, or the lift pump is worn, maybe a fuel tank suction pipe is clogged. I have to check those things on Saturday.

Nevertheless I've also noticed a small leak at the cooling system line (photo), near the coolant crossover pipe. I'm wondering if it can have something in common. Coolant leak is not big, but it intensifies as the engine gets warmer. Maybe there is a pressure sensor or something like that prevents engine form starting?

Regards,
MC

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Check all of above first. Also make sure your batteries are in good condition.
But Hard starting when hot is a common DB2 Mechanical Injection Pump failure.
The next time it will not start when hot. Pour some cold water over the IP. If it starts right up. The problem is a bad pump. Too much clearance in the rotor head assembly.
If you do need a new pump be sure to get one with a new high pressure rotor head assembly.
 

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Discussion Starter · #4 ·
Hi, thank you for your answers. I'll check all those fuel-related things on Saturday. When it comes to the grounds they all are OK - I checked them and repaired some in February. Batteries might be worn, on Saturday I'll borrow a tester to check them out.

But Hard starting when hot is a common DB2 Mechanical Injection Pump failure.
I heard about this and I hope it is not an IP problem, what is more it occured almost overnight. In fact it doesn't happen when engine is hot, it happens about 30 - 60 minutes after shutting off the hot engine, so it is warm but not hot. I have a feeling that it has something to do with glow plugs sequence (are they controlled with temperature?) or this little electric fuel pump - it is hot summer 87 F degree constantly, this pump might be overheating. I'll write more on Saturday.

Regards.
 

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Discussion Starter · #5 ·
BTW, do you hear a lift pump in your trucks running when the glow plugs sequence is over, but the engine is not started yet? In my truck this pump is quiet after the "wait to start" lamp stops blinking.
 

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When you turn the ignition to ON. You should hear the LP run till it times out .In my truck the LP shuts off after 5-10 seconds . This is to prime the system.
After truck is started LP runs continuous.
 
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Load (not voltage) test the batteries one at a time.

Leaking coolant from that quick connect is common.
You can replace it with a barb connector and put a 3/4" heater hose directly on the barb with worm clamp. The direction and part no should be in the thread link above by Ok.
The tricky part will be taking it off without breaking it.

No the coolant leak does not affect the truck starting.
 
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Discussion Starter · #8 ·
When you turn the ignition to ON. You should hear the LP run till it times out .In my truck the LP shuts off after 5-10 seconds . This is to prime the system.
After truck is started LP runs continuous.
My pump works the same way, but I think when the engine is warm it is priming the system only about 1 second. Is the priming time based on a pressure sensor or it works together with glow plugs?

Nevertheless I've ordered a new lift pump and transparent fuel hose to spot if the fuel is free of the air bubbles. I hope packages will be delivered before Saturday, it is the only day I have some time to work with the truck.

Load (not voltage) test the batteries one at a time.
I will have a tester on Saturday. In case one or two batteries are bad, what CCA should I look for? 700A battery will be OK?

No the coolant leak does not affect the truck starting.
Thank you, I thought there could be a pressure sensor and in case of any leak it prevents the engine from starting. I've already seen a solution like that somewhere else.
 

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If one battery is bad, you need to replace both batteries.
Why? the bad battery will take down the good/new battery.

CA should be in the label of the battery itself.
You need an accumulation of around 1200 CA.
 
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Discussion Starter · #10 ·
OK, so today I did some work on the truck.

Firstly I've tested the batteries - they are OK. Then I've checked out for the air bubbles in the fuel system with a method that @OkDually suggested - no air in the fuel. The thing that striked me out was how hard was it to bleed the fuel system after installing a transparent hose. After bleeding the air filter and several priming and long cranking I still had to use a starting spray.

The next thing was to check out a lift pump. The pump's plug has a constant voltage during "wait to start" period and when the engine is working. I can hear the pump during WTS, but for me it's noisy and rattling, nothing like a gasoline pump. During the priming, fuel pressure on a T-valve i about 7 PSI. After opening this valve when idling, the engine sputters and dies within some seconds.

I wanted to replace the pump for a new one, but it occured that nuts are rusty and hard to move. There was a risk of breaking the fuel line, so I've decided for not doing this. It seems I must replace the whole fuel line, but they are impossible to get here in Poland and the cost of shipping it from the USA is bigger then the line itself. My plan is to replace a metal fuel lines (both of them: fuel feed and fuel return) with elastic ones. I've also realized that when the fuel tank was 50 -100% full there was no problem with warm-starting, now I have about 20% of fuel in the tank and the problem intensifies.

Regards,

MC
 

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OK, so today I did some work on the truck.

Firstly I've tested the batteries - they are OK. Then I've checked out for the air bubbles in the fuel system with a method that @OkDually suggested - no air in the fuel. The thing that striked me out was how hard was it to bleed the fuel system after installing a transparent hose. After bleeding the air filter and several priming and long cranking I still had to use a starting spray.

The next thing was to check out a lift pump. The pump's plug has a constant voltage during "wait to start" period and when the engine is working. I can hear the pump during WTS, but for me it's noisy and rattling, nothing like a gasoline pump. During the priming, fuel pressure on a T-valve i about 7 PSI. After opening this valve when idling, the engine sputters and dies within some seconds.

I wanted to replace the pump for a new one, but it occured that nuts are rusty and hard to move. There was a risk of breaking the fuel line, so I've decided for not doing this. It seems I must replace the whole fuel line, but they are impossible to get here in Poland and the cost of shipping it from the USA is bigger then the line itself. My plan is to replace a metal fuel lines (both of them: fuel feed and fuel return) with elastic ones. I've also realized that when the fuel tank was 50 -100% full there was no problem with warm-starting, now I have about 20% of fuel in the tank and the problem intensifies.

Regards,

MC
Do not use starting spray. You can cause severe damage in the engine.
If you must use a spray then use a favorite cooking spray or some WD40.

If you open the t valve with the engine running and the engine dies, that is a sign of a weak lift pump.
 
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Discussion Starter · #12 ·
Do not use starting spray. You can cause severe damage in the engine.
If you must use a spray then use a favorite cooking spray or some WD40.
I know it is not healthy for the engine, but I didn't want to fry up the starter motor. In fact I used a cockpit shine spray. :)

If you open the t valve with the engine running and the engine dies, that is a sign of a weak lift pump.
Good to know, I already own a new one. Today I ordered a flexible fuel lines to replace corroded metal ones in the frame and then I will be able to install a new pump. I would prefer to buy an original fuel lines but I'm not going to pay 200 USD only for the shipping...
 
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