Slow engine warm up

Topic: Slow engine warm up (Read 1216 times) previous topic - next topic

Slow engine warm up

August 16, 2021, 07:50:35 am

When I start the engine in my '98 U295 with the Cummins C8.3, it takes a long time before the water temp gauge on the dash shows any movement. I don't know if "limp mode" is the correct phrase, but I cannot get more than 2,000 RPM out of the engine and just getting out of the campground in the morning is a struggle until the water temp shows 150 degrees, and this can take 15 minutes sitting still at a high idle. Neighbors don't like this. Comments? Runs beautifully the rest of the day.

Re: Slow engine warm up

Reply #1 – August 16, 2021, 08:29:29 am

2000 rpm is about all I ever get too. Redline is not much above that. Not sure why you don't have any getup and go.

Rich

Re: Slow engine warm up

Reply #2 – August 16, 2021, 08:56:58 am

Bad thermostat (I believe there are 2)

Re: Slow engine warm up

Reply #3 – August 16, 2021, 09:34:12 am

You should be good to go as soon as the air pressure is up regardless of the engine temp. I get to 6th gear and highway speeds without reaching 2000 rpm.

But..... ours is a mechanical 8.3

Should not have to get to operating temp before hitting the road because it probably won't get to that temp at idle on a hot day in New Mexico. 😎

Re: Slow engine warm up

Reply #4 – August 16, 2021, 09:51:08 am

As soon as I have air pressure, I'm out of there. Why wait? It's bad for the engine, environment and against the law in many places. Warm it up with moderate driving. Check thermostat by putting hand on radiator. If warm after 5 minutes, the thermostat is bad.

Pierce

Re: Slow engine warm up

Reply #5 – August 16, 2021, 09:58:49 am

I don't understand why the engine would be in "limp mode" until it warms up. Why is he not getting any power even though he gets 2000 rpm?

Rich

Re: Slow engine warm up

Reply #6 – August 16, 2021, 10:04:09 am

When I had coach with a 8.3 engine it was low on power until I went a block or two
and it started to warm up.

Re: Slow engine warm up

Reply #7 – August 16, 2021, 05:08:54 pm

Quote from: Rich Bowman – August 16, 2021, 08:29:29 am

2000 rpm is about all I ever get too. Redline is not much above that. Not sure why you don't have any getup and go.
Rich

How do you define "redline?" Normal cruising at 65mph is about 2,400 and it's not uncommon to see 3,000 when accelerating.

Re: Slow engine warm up

Reply #8 – August 16, 2021, 05:13:43 pm

Redline is the max rpm of an engine,if you go past ,valves start to break and bend.Our mechanical 8.3 cruises at 65 only at around
1900 rpm.

Re: Slow engine warm up

Reply #9 – August 16, 2021, 05:19:09 pm

Quote from: John44 – August 16, 2021, 05:13:43 pm

Redline is the max rpm of an engine,if you go past ,valves start to break and bend.Our mechanical 8.3 cruises at 65 only at around
1900 rpm.

So how would I prevent the RPM's from going as high as they do?

Re: Slow engine warm up

Reply #10 – August 16, 2021, 05:19:28 pm

Quote from: Dan & Annie – August 16, 2021, 05:08:54 pm

How do you define "redline?" Normal cruising at 65mph is about 2,400 and it's not uncommon to see 3,000 when accelerating.

Suspect your tach is way off.

Do you have a Scan Gauge D, silverleaf or other engine monitoring system? What RPM does it show compared with the tach?

Re: Slow engine warm up

Reply #11 – August 16, 2021, 05:22:57 pm

Do what Brett suggests,think your tach is reading wrong rpm.

Re: Slow engine warm up

Reply #12 – August 16, 2021, 05:30:53 pm

Quote from: wolfe10 – August 16, 2021, 05:19:28 pm

Suspect your tach is way off.
Do you have a Scan Gauge D, silverleaf or other engine monitoring system? What RPM does it show compared with the tach?

I won't say that the tach is not wrong, but it was new in November 2020, installed by MOT.
Do these monitoring systems work on a '98 C8.3? If I have an OBD2 port, I haven't found it. Where is it?

Re: Slow engine warm up

Reply #13 – August 16, 2021, 05:53:04 pm

Neiko 20713A Digital Tachometer, Non Contact Laser Photo | 2.5 - 99,999 RPM...

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Re: Slow engine warm up

Reply #14 – August 16, 2021, 05:58:18 pm

Quote from: Dan & Annie – August 16, 2021, 05:30:53 pm

I won't say that the tach is not wrong, but it was new in November 2020, installed by MOT.
Do these monitoring systems work on a '98 C8.3? If I have an OBD2 port, I haven't found it. Where is it?

Under dash by the left driver's knee on ours. Yours may be different. It may have a cover on it.

Pierce

Re: Slow engine warm up

Reply #15 – August 16, 2021, 06:34:40 pm

I don't understand & picture what you are saying... Engine RPM is about max RPM. Does your transmission shift as you drive? Are you afraid to drive normal speed no mater what coolant temp reads. Are you reading trans temp?

Is this something new or is coach new to you?

Re: Slow engine warm up

Reply #16 – August 16, 2021, 06:47:17 pm

Quote from: Dan & Annie – August 16, 2021, 05:08:54 pm

Normal cruising at 65mph is about 2,400 and it's not uncommon to see 3,000 when accelerating.

IMO your tach is definitely not reading correct RPM.

With a Cummins C8.3-325 the horsepower is rated at 2200 RPM and the governed speed is 2400 RPM. You should not see over 2400 RPM in normal driving even when accelerating with full throttle. I am pretty sure you will never see 3000 RPM under any conditions.

The .pdf file below lists the engine data for the C8.3-325:

Re: Slow engine warm up

Reply #17 – August 16, 2021, 09:12:13 pm

VMspc will not work with the C8.3. It is a non-electronic engine. No engine data available. Not until the ISC8.3.

Re: Slow engine warm up

Reply #18 – August 16, 2021, 09:53:00 pm

What brand is your tach? Many DO have to be calibrated.

Re: Slow engine warm up

Reply #19 – August 16, 2021, 10:21:20 pm

Getting back to the purpose of my original post, let me restate.
My usual routine: Start the coach in the morning, shut the HWH leveling off, let air pressure build until pop off, oil pressure up around 60, do my walk around outside, sit down and drive away.
I've done 12,000 miles since November, and four times, including twice in the last week, this has happened: Maximum achievable speed driving out of the campground, or accelerating out of Walmart onto the main road, is 3 mph. If there is any kind of an incline I cannot even get to that. Almost a dead stop. Only these last two times did I happened to notice the water temp, and both times the problem went away immediately at 150 degrees.
The Cummins manual, page 1-4, tells me that coolant temp must stay above 140 degrees in order for fuel to burn completely, but like I said, it can take 15 minutes for me to reach that temp.
If I have a bad thermostat, how do I check and change that?

Re: Slow engine warm up

Reply #20 – August 16, 2021, 10:24:01 pm

Quote from: wolfe10 – August 16, 2021, 09:53:00 pm

What brand is your tach? Many DO have to be calibrated.

New speedo and tach are VDO.

Re: Slow engine warm up

Reply #21 – August 16, 2021, 10:28:40 pm

I could easily be wrong but doubt your lack of power is due to engine temperature.
What does your exhaust look like when trying to limp at 3 mph?

Re: Slow engine warm up

Reply #22 – August 16, 2021, 10:49:58 pm

I agree with Dakota Slim - I don't think engine temp has anything to do with your problem. The mechanical C8.3 engine doesn't have any kind of computer control that would respond to low engine coolant temp. On our coach, if air pressure is up, I could crank the engine and drive off immediately with a dead-cold engine - no problem.

I would look at the throttle control system.

What type throttle do you have - Bendix air throttle, or King Controls.

If King Controls, see threads linked below for possible ideas:

King Control problem

Low Power From Engine

Re: Slow engine warm up

Reply #23 – August 17, 2021, 07:42:23 am

Quote from: Dakota Slim – August 16, 2021, 10:28:40 pm

I could easily be wrong but doubt your lack of power is due to engine temperature.
What does your exhaust look like when trying to limp at 3 mph?

Agree..... engine temp SHOULD have nothing to do with his lack of power. Sounds like a engine speed sensor or tach feedback issue. Engine isn't revving as high as the tach shows. At least that's what it appears to be from a armchair quarterback position. 😎

Re: Slow engine warm up

Reply #24 – August 17, 2021, 08:06:38 am

Quote from: Chuck & Jeannie – August 16, 2021, 10:49:58 pm

I would look at the throttle control system.

What type throttle do you have - Bendix air throttle, or King Controls.

If King Controls, see threads linked below for possible ideas:

King Control problem

Low Power From Engine

I have King Controls throttle.
After reading through all the links here, there are SO MANY possibilities! The next time I experience this problem, I have lots of things to check. Between now and then - lots of re-reading and taking notes and making a checklist. Fuel filters, air intake, brake light wiring, fuel solenoid...

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